Quarterly report pursuant to Section 13 or 15(d)

Schedule of Repurchase Agreements by Maturity (Details)

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Schedule of Repurchase Agreements by Maturity (Details) - USD ($)
$ in Thousands
Mar. 31, 2019
Dec. 31, 2018
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements $ 19,729,691 $ 23,133,476
Weighted average borrowing rate 2.85% 2.68%
US Government Agencies Debt Securities [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements $ 17,202,959 $ 20,091,396
Weighted average borrowing rate 2.71% 2.52%
Mortgage-backed Securities, Issued by Private Enterprises [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements $ 2,180,425 $ 2,695,564
Weighted average borrowing rate 3.74% 3.65%
Inverse Interest-Only Securities [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements $ 46,307 $ 46,516
Weighted average borrowing rate 3.51% 3.34%
Mortgage Servicing Rights [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements $ 300,000 $ 300,000
Weighted average borrowing rate 4.25% 4.51%
Maturity up to 30 days [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements $ 4,852,492 $ 7,488,869
Maturity up to 30 days [Member] | US Government Agencies Debt Securities [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements 3,900,686 6,712,021
Maturity up to 30 days [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements 931,231 770,287
Maturity up to 30 days [Member] | Inverse Interest-Only Securities [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements 20,575 6,561
Maturity up to 30 days [Member] | Mortgage Servicing Rights [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements 0 0
Maturity 30 to 59 Days [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements 3,996,887 5,077,598
Maturity 30 to 59 Days [Member] | US Government Agencies Debt Securities [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements 3,577,461 4,557,688
Maturity 30 to 59 Days [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements 407,568 496,466
Maturity 30 to 59 Days [Member] | Inverse Interest-Only Securities [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements 11,858 23,444
Maturity 30 to 59 Days [Member] | Mortgage Servicing Rights [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements 0 0
Maturity 60 to 89 Days [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements 4,814,169 5,655,061
Maturity 60 to 89 Days [Member] | US Government Agencies Debt Securities [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements 4,462,064 5,410,967
Maturity 60 to 89 Days [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements 352,105 242,473
Maturity 60 to 89 Days [Member] | Inverse Interest-Only Securities [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements 0 1,621
Maturity 60 to 89 Days [Member] | Mortgage Servicing Rights [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements 0 0
Maturity 90 to 119 Days [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements 2,790,671 1,938,859
Maturity 90 to 119 Days [Member] | US Government Agencies Debt Securities [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements 2,405,034 1,209,395
Maturity 90 to 119 Days [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements 385,637 722,399
Maturity 90 to 119 Days [Member] | Inverse Interest-Only Securities [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements 0 7,065
Maturity 90 to 119 Days [Member] | Mortgage Servicing Rights [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements 0 0
Maturity 120 to 364 days [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements 2,975,472 2,673,089
Maturity 120 to 364 days [Member] | US Government Agencies Debt Securities [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements 2,857,714 2,201,325
Maturity 120 to 364 days [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements 103,884 463,939
Maturity 120 to 364 days [Member] | Inverse Interest-Only Securities [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements 13,874 7,825
Maturity 120 to 364 days [Member] | Mortgage Servicing Rights [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements 0 0
Maturity Over One Year [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements 300,000 300,000
Maturity Over One Year [Member] | US Government Agencies Debt Securities [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements 0 0
Maturity Over One Year [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements 0 0
Maturity Over One Year [Member] | Inverse Interest-Only Securities [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements 0 0
Maturity Over One Year [Member] | Mortgage Servicing Rights [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Repurchase agreements $ 300,000 $ 300,000