Derivative Instruments - Schedule of settlement of fair value hedges (Details) - Fair value hedging - Deposit liabilities - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Derivative [Line Items]
Cumulative reduction to interest expense	$ 117,818	$ 108,449
Remaining balance	$ 115,377	$ 124,746
Weighted average years remaining to maturity	19 years 4 months 24 days	20 years 9 months 18 days