Quarterly report pursuant to Section 13 or 15(d)

Fair Value by Balance Sheet Grouping (Details)

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Fair Value by Balance Sheet Grouping (Details) - USD ($)
$ in Thousands
Sep. 30, 2018
Jun. 30, 2018
Dec. 31, 2017
Sep. 30, 2017
Jun. 30, 2017
Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]            
Available-for-sale securities, at fair value $ 25,938,916   $ 21,220,819      
Mortgage servicing rights, at fair value 1,664,024 $ 1,450,261 1,086,717 $ 930,613 $ 898,025 $ 693,815
Residential mortgage loans held-for-sale, at fair value 27,537   30,414 $ 31,197   $ 40,146
Cash and cash equivalents 422,851   419,159      
Restricted cash 888,632   635,836      
Derivative assets, at fair value 403,231   309,918      
Reverse repurchase agreements 759,375   0      
Equity securities, at fair value 0   29,413      
Federal Home Loan Bank stock 40,848   53,826      
Equity investments 6,529   3,000      
Repurchase agreements 23,806,631   19,451,207      
Federal Home Loan Bank advances 865,024   1,215,024      
Revolving credit facilities 310,000   20,000      
Convertible senior notes 283,555   282,827      
Convertible senior notes, at fair value 296,312   306,351      
Derivative liabilities, at fair value 797,504   31,903      
Federal Home Loan Bank of Des Moines [Member]            
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]            
Federal Home Loan Bank stock 40,800   53,800      
Federal Home Loan Bank advances $ 900,000   $ 1,200,000