Derivatives - Derivatives Associated With Interest Rate Risk Management Activities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Customer Interest Rate Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional	$ 2,697,522	$ 2,271,448
Assets	65,768	18,744
Liabilities	6,858	27,768
Offsetting Upstream Interest Rate Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional	2,697,522	2,271,448
Assets	2,583	4,014
Liabilities	3,994	9,041
Customer Interest Rate Contracts Hedging | Hedging Instruments And Hedged Items | Customer Interest Rate Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional	3,044,067	2,029,162
Assets	90,394	20,262
Liabilities	3,515	25,880
Customer Interest Rate Contracts Hedging | Hedging Instruments And Hedged Items | Offsetting Upstream Interest Rate Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional	3,044,067	2,029,162
Assets	3,537	8,154
Liabilities	9,735	9,153
Debt Hedging | Hedging Instruments And Hedged Items | Interest Rate Swaps
Derivative Instruments, Gain (Loss) [Line Items]
Notional	500,000	900,000
Assets		127
Liabilities	69	6
Debt Hedging | Hedging Instruments And Hedged Items | Par
Derivative Instruments, Gain (Loss) [Line Items]
Term borrowings	500,000	900,000
Debt Hedging | Hedging Instruments And Hedged Items | Cumulative fair value hedging adjustments
Derivative Instruments, Gain (Loss) [Line Items]
Term borrowings	(1,604)	(15,094)
Debt Hedging | Hedging Instruments And Hedged Items | Unamortized premium/(discount) and issuance costs
Derivative Instruments, Gain (Loss) [Line Items]
Term borrowings	(740)	(2,295)
Debt Hedging | Hedging Instruments And Hedged Items | Term Borrowings
Derivative Instruments, Gain (Loss) [Line Items]
Term borrowings	$ 497,656	$ 882,611