Short and Long-term Funding, Composition (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Short-term Debt [Line Items]
Federal funds purchased	$ 362,000	$ 19,710
Securities sold under agreements to repurchase	71,097	91,941
Federal funds purchased and securities sold under agreements to repurchase	433,097	111,651
Commercial paper	32,016	45,423
Total short-term funding	465,113	157,074
Debt Instrument [Line Items]
Corporation subordinated notes, at par, due 2025	250,000	250,000
Finance Lease, Liability	2,209	0
Other Long-term Debt and Capitalized Costs	(2,866)	(4,389)
Other Long-term Debt	549,343	795,611
TotalShortTermLongTermExcludingFHLB	1,014,456	952,685
Advances from Federal Home Loan Banks [Abstract]
Short-term FHLB advances	520,000	900,000
Long-term FHLB advances	2,660,967	2,674,371
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Amount of Advances	3,180,967	3,574,371
Debt, Long-term and Short-term, Combined Amount [Abstract]
Debt, Long-term and Short-term, Combined Amount, Total	4,195,422	4,527,056
Corporation senior notes, at par, due 2019
Debt Instrument [Line Items]
Senior Notes	0	250,000
Bank senior notes, at par, due 2021
Debt Instrument [Line Items]
Senior Notes	$ 300,000	$ 300,000