Annual report pursuant to Section 13 and 15(d)

Derivative Instruments and Hedging Activities Interest Rate Sensitive Assets/Liabilities (Details)

v3.8.0.1
Derivative Instruments and Hedging Activities Interest Rate Sensitive Assets/Liabilities (Details) - USD ($)
$ in Thousands
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Derivatives, Fair Value [Line Items]        
Available-for-sale securities, at fair value $ 21,220,819 $ 13,116,171    
Mortgage servicing rights, at fair value 1,086,717 693,815 $ 493,688 $ 452,006
Interest-Only-Strip [Member]        
Derivatives, Fair Value [Line Items]        
Available-for-sale securities, at fair value $ 117,826 $ 71,084