Fair Value - Financial Instruments not Required to be Carried at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Financial assets:
Held-to-maturity investment securities, fair value	$ 3,433,029	$ 3,814,822
Lease and lease commitments excluded
Financing leases	332,500	298,100
Deposit liabilities with no defined or contractual maturity	17,900,000	19,200,000
Book Value
Financial assets:
Cash and cash equivalents	1,213,428	526,624
Held-to-maturity investment securities, fair value	4,104,114	4,320,639
Loans	13,999,820	13,793,922
Financial liabilities:
Time deposits	3,661,131	2,476,050
Short-term borrowings	500,000	75,000
Estimated Fair Value
Financial assets:
Cash and cash equivalents	1,213,428	526,624
Held-to-maturity investment securities, fair value	3,433,029	3,814,822
Loans	13,166,377	13,138,787
Financial liabilities:
Time deposits	3,625,116	2,423,231
Short-term borrowings	495,306	74,991
Estimated Fair Value | Quoted Prices in Active Markets for Identical Assets (Level 1)
Financial assets:
Cash and cash equivalents	246,028	297,502
Estimated Fair Value | Significant Other Observable Inputs (Level 2)
Financial assets:
Cash and cash equivalents	967,400	229,122
Held-to-maturity investment securities, fair value	3,433,029	3,814,822
Financial liabilities:
Time deposits	3,625,116	2,423,231
Short-term borrowings	495,306	74,991
Estimated Fair Value | Significant Unobservable Inputs (Level 3)
Financial assets:
Loans	$ 13,166,377	$ 13,138,787