Derivatives - Narrative (Details) - USD ($) $ in Thousands		3 Months Ended				6 Months Ended
	Nov. 01, 2019	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2017	Mar. 31, 2016	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Collateral cash payables		$ 361,087				$ 361,087		$ 145,334
Total trading revenues		100,300	$ 54,500			178,600	$ 99,000
Cash flow hedge length of time					5 years
Hedged amount of foreign currency denominated loans		13,800				13,800		18,400
Derivative assets (Note 14)		599,445				599,445		182,984
Derivative liability		75,226				75,226		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		18,000				18,000		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		253,700				253,700		63,100
Net fair value of derivative liabilities with adjustable posting thresholds		3,800				3,800		6,400
Collateral received		340,000				340,000		148,500
Securities posted collateral		43,500				43,500		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		253,600				253,600		63,100
Net fair value of derivative liabilities with adjustable posting thresholds		25,500				25,500		10,300
Collateral received		340,000				340,000		148,500
Securities posted collateral		65,100				65,100		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		230,200				230,200		136,600
Collateral cash payables		130,600				130,600		53,000
Senior Subordinated Notes | Senior Debt Maturing In December 2019
Derivative Instruments, Gain (Loss) [Line Items]
Term borrowings		400,000				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				500,000
Derivatives, interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Collateral cash payables		348,497				348,497		143,334
Derivative assets (Note 14)		564,037				564,037		162,344
Derivative liability		44,743				44,743		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				700,000		$ 900,000
Credit Risk Contract
Derivative Instruments, Gain (Loss) [Line Items]
Derivative asset, notional amount		93,800				93,800
Derivative liability, notional amount		246,100				246,100
Derivative assets (Note 14)		170				170
Derivative liability		$ 830				$ 830