Annual report pursuant to Section 13 and 15(d)

Schedule of Underlying Assets of Repurchase Agreements when Amount of Repurchase Agreements Exceeds 10 Percent of Assets (Details)

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Schedule of Underlying Assets of Repurchase Agreements when Amount of Repurchase Agreements Exceeds 10 Percent of Assets (Details) - USD ($)
$ in Thousands
Dec. 31, 2017
Dec. 31, 2016
Assets Sold under Agreements to Repurchase [Line Items]    
Assets pledged or restricted as collateral for repurchase agreements $ 21,501,250 $ 10,092,048
Available-for-sale Securities [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Assets pledged or restricted as collateral for repurchase agreements 19,780,175 9,528,163
Servicing Contracts [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Assets pledged or restricted as collateral for repurchase agreements 424,740 0
Retained Interest [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Assets pledged or restricted as collateral for repurchase agreements 0 211,095
Cash and Cash Equivalents [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Assets pledged or restricted as collateral for repurchase agreements 15,000 15,000
Restricted Cash and Cash Equivalents [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Assets pledged or restricted as collateral for repurchase agreements 417,018 162,759
Due From Correspondent Brokers [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Assets pledged or restricted as collateral for repurchase agreements 773,422 48,690
Derivative Financial Instruments, Assets [Member]    
Assets Sold under Agreements to Repurchase [Line Items]    
Assets pledged or restricted as collateral for repurchase agreements $ 90,895 $ 126,341