Derivatives - Gains/(Losses) on Derivatives Associated with Interest Rate Risk Management Activities (Details) - Hedging Instruments And Hedged Items - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Customer Interest Rate Contracts Hedging | Customer interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) related to interest rate derivatives	$ 50,706	$ (4,459)	$ 79,818	$ (29,183)
Customer Interest Rate Contracts Hedging | Offsetting upstream interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) related to interest rate derivatives	(50,706)	4,459	(79,818)	29,183
Debt Hedging | Interest Rate Swap
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) related to interest rate derivatives	6,697	(1,545)	10,976	(8,140)
Debt Hedging | Term Borrowings
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(Losses) related to term borrowings	$ (6,605)	$ 1,520	$ (10,871)	$ 8,070