Derivatives and Hedging Activities - Gain (Loss) Recognized in Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Loans [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net gain (loss) recognized on derivatives, including economic hedge	$ 14,125	$ (1,499)
Servicing contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net gain (loss) recognized on derivatives, including economic hedge	(30,977)	379
Mortgages [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net gain (loss) recognized on derivatives, including economic hedge	$ (16,852)	$ (1,120)