Derivatives - Gains/(Losses) on Derivatives Associated with Interest Rate Risk Management Activities (Details) - Hedging Instruments And Hedged Items - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Customer Interest Rate Contracts Hedging | Customer interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) related to interest rate derivatives	$ 44,375	$ (10,620)	$ 124,193	$ (39,803)
Customer Interest Rate Contracts Hedging | Offsetting upstream interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) related to interest rate derivatives	(44,375)	10,620	(124,193)	39,803
Debt Hedging | Interest Rate Swap
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) related to interest rate derivatives	1,994	(246)	12,969	(8,386)
Debt Hedging | Term Borrowings
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(Losses) related to term borrowings	$ (2,004)	$ 240	$ (12,876)	$ 8,310