CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities
Net income	$ 265,735	$ 185,754	$ 284,392
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for credit losses	(39,000)	121,718	13,800
Depreciation, amortization and accretion, net	51,844	63,071	67,824
Deferred income tax provision (benefits)	14,120	(19,396)	17,060
Stock-based compensation	13,106	10,028	7,826
Other (gains) losses	(1,437)	(4)	19
Originations of loans held for sale	(87,336)	(327,076)	(19,164)
Proceeds from sales of loans held for sale	100,499	326,785	18,156
Net gains on sales of loans originated for investment and held for sale	(2,706)	(18,995)	1,102
Net (gains) losses on investment securities	(102)	114	2,715
Change in assets and liabilities:
Net increase in other assets	(8,211)	(17,880)	(20,923)
Net increase (decrease) in other liabilities	110,613	(114,613)	(76,303)
Net cash provided by operating activities	417,125	209,506	296,504
Available-for-sale securities:
Proceeds from maturities and principal repayments	1,814,514	1,474,587	767,892
Proceeds from calls and sales	11,115	644,983	1,070,715
Purchases	(4,428,656)	(4,045,871)	(1,301,041)
Other investments:
Proceeds from sales	28,483	34,822	14,292
Purchases	(80,464)	(77,927)	(30,996)
Loans:
Net decrease (increase) in loans and leases resulting from originations and principal repayments	594,642	(217,530)	(133,702)
Proceeds from sales of loans originated for investment	2,200	153,647	407,698
Purchases of loans	(309,760)	(41,146)	(398,735)
Proceeds from bank-owned life insurance	7,903	3,089	7,682
Purchases of premises, equipment and software	(20,458)	(33,390)	(29,354)
Proceeds from sales of premises and equipment	4,021
Proceeds from sales of other real estate owned	141	787	759
Other		186	2
Net cash (used in) provided by investing activities	(2,376,319)	(2,103,763)	375,212
Cash flows from financing activities
Net increase (decrease) in deposits	2,588,423	2,782,729	(705,074)
Repayment of short-term borrowings		(400,000)
Repayment of long-term borrowings	(200,010)	(9)	(10)
Dividends paid	(134,133)	(135,099)	(138,246)
Stock tendered for payment of withholding taxes	(3,108)	(1,749)	(1,764)
Proceeds from employee stock purchase plan	547	312
Common stock repurchased	(75,000)	(5,000)	(136,242)
Net cash provided by (used in) financing activities	2,176,719	2,241,184	(981,336)
Net increase (decrease) in cash and cash equivalents	217,525	346,927	(309,620)
Cash and cash equivalents at beginning of year	1,040,944	694,017	1,003,637
Cash and cash equivalents at end of year	1,258,469	1,040,944	694,017
Supplemental disclosures
Interest paid	23,001	52,865	102,457
Income taxes paid, net of income tax refunds	55,354	53,272	70,508
Noncash investing and financing activities:
Transfers from loans and leases to other real estate owned	316	437	310
Operating lease right-of-use assets obtained in exchange for new lease obligations	31,792	3,796	1,401
Transfers from loans and leases and other assets to other real estate owned	1,616	145,036	408,264
Obligation to fund low-income housing partnerships	$ 35,721	$ 13,767	$ 31,628