Derivatives - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Collateral cash payables	$ 347,000	$ 145,000
Total trading revenues	371,000	228,000	$ 132,000
Term borrowings	1,670,000	791,000
Hedged amount of foreign currency denominated loans	12,000	18,000
Derivative asset	765,000	183,000
Derivative liabilities, other	125,000	44,000
Visa Class B Shares
Derivative Instruments, Gain (Loss) [Line Items]
Derivative liabilities related to sale	13,000	23,000
Additional Derivative Agreements | Derivative Instruments With Adjustable Collateral Posting Thresholds
Derivative Instruments, Gain (Loss) [Line Items]
Net fair value of derivative assets with adjustable posting thresholds	200,000	63,000
Net fair value of derivative liabilities with adjustable posting thresholds	5,000	6,000
Collateral received	320,000	149,000
Securities posted collateral	34,000	18,000
Additional Derivative Agreements | Derivative Instruments With Accelerated Termination Provisions
Derivative Instruments, Gain (Loss) [Line Items]
Net fair value of derivative assets with adjustable posting thresholds	216,000	63,000
Net fair value of derivative liabilities with adjustable posting thresholds	17,000	10,000
Collateral received	343,000	149,000
Securities posted collateral	53,000	23,000
Interest Rate Contract
Derivative Instruments, Gain (Loss) [Line Items]
Collateral cash payables	327,000	143,000
Derivative asset	702,000	162,000
Derivative liabilities, other	60,000	24,000
Interest Rate Contract | Cash Flow Hedges | Hedged Items
Derivative Instruments, Gain (Loss) [Line Items]
Variability in cash flows related to debt instruments (primarily loans)	1,500,000	900,000
Credit Risk Contract
Derivative Instruments, Gain (Loss) [Line Items]
Derivative asset, notional amount	233,000
Derivative liability, notional amount	464,000
Derivative asset	280
Derivative liabilities, other	820
Embedded Derivative Financial Instruments
Derivative Instruments, Gain (Loss) [Line Items]
Derivative asset	1,000
Derivative liabilities, other	1,000
Counterparties
Derivative Instruments, Gain (Loss) [Line Items]
Collateral cash receivables	280,000	137,000
Collateral cash payables	166,000	$ 53,000
Senior Subordinated Notes | Senior Debt Maturing In December 2019 | Long Term Debt Hedged With Fair Value Interest Rate Derivatives Using Long Haul Method
Derivative Instruments, Gain (Loss) [Line Items]
Term borrowings	400,000
Debt redeemed	400,000
Senior Subordinated Notes | Senior Debt Maturing In December 2020 | Long Term Debt Hedged With Fair Value Interest Rate Derivatives Using Long Haul Method
Derivative Instruments, Gain (Loss) [Line Items]
Term borrowings	500,000
Debt redeemed	$ 500,000