Derivatives - Derivatives Associated With Interest Rate Risk Management Activities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Customer interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional	$ 3,667,914	$ 2,697,522
Assets	254,246	65,768
Liabilities	1,827	6,858
Offsetting upstream interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional	3,667,914	2,697,522
Assets	7,454	2,583
Liabilities	17,667	3,994
Customer Interest Rate Contracts Hedging | Hedging Instruments And Hedged Items | Customer interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional	3,679,991	3,044,067
Assets	297,233	90,394
Liabilities	258	3,515
Customer Interest Rate Contracts Hedging | Hedging Instruments And Hedged Items | Offsetting upstream interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional	3,679,991	3,044,067
Assets	4,877	3,537
Liabilities	24,922	9,735
Debt Hedging | Hedging Instruments And Hedged Items | Interest Rate Swap
Derivative Instruments, Gain (Loss) [Line Items]
Notional	500,000	500,000
Assets	27
Liabilities		69
Debt Hedging | Hedging Instruments And Hedged Items | Term Borrowings, Par
Derivative Instruments, Gain (Loss) [Line Items]
Term borrowings	500,000	500,000
Debt Hedging | Hedging Instruments And Hedged Items | Term Borrowings, Cumulative Fair Value Hedging Adjustments
Derivative Instruments, Gain (Loss) [Line Items]
Term borrowings	2,142	(1,604)
Debt Hedging | Hedging Instruments And Hedged Items | Term Borrowings, Unamortized Premium (Discount) and Issuance Costs
Derivative Instruments, Gain (Loss) [Line Items]
Term borrowings	(296)	(740)
Debt Hedging | Hedging Instruments And Hedged Items | Term Borrowings
Derivative Instruments, Gain (Loss) [Line Items]
Term borrowings	$ 501,846	$ 497,656