Fair Value of Financial Instruments - Carrying Amount and Estimated Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands		Sep. 30, 2023		Dec. 31, 2022
Financial assets:
Securities purchased with agreement to resell		$ 500,000		$ 513,276
Securities held-to-maturity		2,581,232		2,744,946
Quoted market prices in an active market (Level 1)
Financial assets:
Securities purchased with agreement to resell		0		0
Securities held-to-maturity		0		0
Loans, net		0		0
Consumer loans held-for-sale		0		0
Commercial loans held-for-sale		0		0
Financial liabilities:
Deposits and securities sold under agreements to repurchase		0		0
Federal Home Loan Bank advances		0		0
Subordinated debt and other borrowings		0		0
Models with significant observable market parameters (Level 2)
Financial assets:
Securities purchased with agreement to resell		0		0
Securities held-to-maturity		2,581,232		2,744,946
Loans, net		0		0
Consumer loans held-for-sale		119,678		42,353
Commercial loans held-for-sale		20,545		21,151
Financial liabilities:
Deposits and securities sold under agreements to repurchase		0		0
Federal Home Loan Bank advances		0		0
Subordinated debt and other borrowings		0		0
Models with significant unobservable market parameters (Level 3)
Financial assets:
Securities purchased with agreement to resell		449,620		440,390
Securities held-to-maturity		0		0
Loans, net		30,375,663		27,901,662
Consumer loans held-for-sale		0		0
Commercial loans held-for-sale		0		0
Financial liabilities:
Deposits and securities sold under agreements to repurchase		37,240,824		34,435,447
Federal Home Loan Bank advances		2,114,924		477,673
Subordinated debt and other borrowings		457,802		430,884
Carrying Amount
Financial assets:
Securities purchased with agreement to resell		500,000		513,276
Securities held-to-maturity		3,018,579		3,079,050
Loans, net		31,597,092		28,740,940
Consumer loans held-for-sale		119,489		42,237
Commercial loans held-for-sale		20,513		21,093
Financial liabilities:
Deposits and securities sold under agreements to repurchase		38,491,808		35,156,148
Federal Home Loan Bank advances		2,110,598		464,436
Subordinated debt and other borrowings		424,718		424,055
Estimated Fair Value
Financial assets:
Securities purchased with agreement to resell		449,620	[1]	440,390
Securities held-to-maturity	[1]	2,581,232		2,744,946
Loans, net	[1]	30,375,663		27,901,662
Consumer loans held-for-sale	[1]	119,678		42,353
Commercial loans held-for-sale	[1]	20,545		21,151
Financial liabilities:
Deposits and securities sold under agreements to repurchase	[1]	37,240,824		34,435,447
Federal Home Loan Bank advances	[1]	2,114,924		477,673
Subordinated debt and other borrowings	[1]	$ 457,802		$ 430,884

[1] Estimated fair values are consistent with an exit-price concept. The assumptions used to estimate the fair values are intended to approximate those that a market-participant would realize in a hypothetical orderly transaction.