Derivatives - Narrative (Details) - USD ($) $ in Thousands		3 Months Ended
	Nov. 01, 2019	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Collateral cash payables		$ 357,816				$ 145,334
Total trading revenues		78,400	$ 44,500
Cash flow hedge length of time					5 years
Hedged amount of foreign currency denominated loans		16,200				18,400
Derivative assets (Note 14)		695,853				182,984
Derivative liability		213,584				44,238
Cash Flow Hedge | Hedged Items
Derivative Instruments, Gain (Loss) [Line Items]
Variability in cash flows related to debt instruments (primarily loans)					$ 250,000
Notional				$ 650,000
Derivative, expired during period		200,000
Visa Class B Shares
Derivative Instruments, Gain (Loss) [Line Items]
Derivative liabilities related to sale		20,400				22,800
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		232,500				63,100
Net fair value of derivative liabilities with adjustable posting thresholds		4,400				6,400
Collateral received		291,300				148,500
Securities posted collateral		41,400				18,400
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		232,300				63,100
Net fair value of derivative liabilities with adjustable posting thresholds		24,200				10,300
Collateral received		291,400				148,500
Securities posted collateral		62,500				22,700
Minimum | Cash Flow Hedge | Hedged Items
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, term of contract				3 years
Maximum | Cash Flow Hedge | Hedged Items
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, term of contract				7 years
Counterparties
Derivative Instruments, Gain (Loss) [Line Items]
Collateral cash receivables		214,400				136,600
Collateral cash payables		160,700				53,000
Senior Subordinated Notes | Senior Debt Maturing In December 2019
Derivative Instruments, Gain (Loss) [Line Items]
Term borrowings		400,000
Debt redeemed	$ 400,000
Senior Subordinated Notes | Senior Debt Maturing In December 2020
Derivative Instruments, Gain (Loss) [Line Items]
Term borrowings		500,000
Derivatives, interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Collateral cash payables		303,798				143,334
Derivative assets (Note 14)		530,337				162,344
Derivative liability		41,980				24,431
Derivatives, interest rate contracts | Cash Flow Hedge | Hedged Items
Derivative Instruments, Gain (Loss) [Line Items]
Variability in cash flows related to debt instruments (primarily loans)		700,000				$ 900,000
Credit Risk Contract
Derivative Instruments, Gain (Loss) [Line Items]
Derivative asset, notional amount		120,800
Derivative liability, notional amount		226,700
Derivative assets (Note 14)		280
Derivative liability		$ 780