Unaudited Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating activities
Net income	$ 47,663	$ 8,445
Adjustments to reconcile net income to net cash provided by operating activities
(Release of) provision for loan losses	(580)	28,600
Depreciation and amortization	3,283	4,318
(Accretion) amortization of net loan costs and premiums, net	(6,859)	795
Deferred income tax expense	5,118	4,641
Amortization of investment security premiums and discounts	3,277	791
Right-of-use asset amortization	2,862	3,615
Net gain on sale of securities available for sale	(1,164)	(122)
Amortization of gains from terminated interest rate swaps	(8,274)	0
Employee Stock Ownership Plan expense	2,080	0
Other	(557)	(576)
Trading securities	0	309
Loans held for sale	(863)	(2,866)
Prepaid pension expense	838	(30,473)
Other assets	43,683	(61,071)
Other liabilities	(25,597)	12,043
Net cash provided by (used in) operating activities	64,910	(31,551)
Investing activities
Proceeds from sales of securities available for sale	23,236	5,600
Proceeds from maturities and principal paydowns of securities available for sale	214,085	56,021
Purchases of securities available for sale	(1,137,969)	(70,301)
Proceeds from sale of Federal Home Loan Bank stock	0	749
Purchases of Federal Home Loan Bank stock	0	(527)
Contributions to low income housing tax credit investments	(2,727)	(5,177)
Contributions to other equity investments	0	(137)
Distributions from equity investments	7	13
Net increase in outstanding loans	(171,325)	(101,856)
Purchased banking premises and equipment, net	(719)	(1,029)
Proceeds from sale of premises held for sale	736	0
Net cash used in investing activities	(1,074,676)	(116,644)
Financing activities
Net increase in demand, savings, interest checking, and money market investment deposit accounts	840,423	762,049
Net decrease in time deposits	(15,332)	(4,430)
Net decrease (increase) in borrowed funds	1,302	(203,968)
Contingent consideration paid	(41)	(92)
Payment of initial public offering costs	0	(1,517)
Dividends declared and paid to common shareholders	(10,324)	0
Net cash provided by financing activities	816,028	552,042
Net (decrease) increase in cash, cash equivalents, and restricted cash	(193,738)	403,847
Cash, cash equivalents, and restricted cash at beginning of period	2,054,070	362,602
Cash, cash equivalents, and restricted cash at end of period	1,860,332	766,449
Supplemental Cash Flow Information [Abstract]
Interest paid	1,049	6,908
Income taxes	4,858	5,361
Noncash Investing and Financing Items [Abstract]
Net increase in capital commitments relating to low income housing tax credit projects	2,943	5,000
Initial recognition of operating lease right-of-use assets upon adoption of Accounting Standards Update 2016-02	0	92,948
Initial recognition of operating lease liabilities upon adoption of Accounting Standards Update 2016-02	$ 0	$ 96,426