Consolidated Statements of Cash Flows $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Operating activities:
Net income	$ 113,320	$ 147,918	$ 134,743
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for credit losses	153,180	25,560	13,170
Depreciation of premises and equipment, net	14,999	15,852	8,329
(Accretion) amortization of fees, premiums and discounts, net	(60,159)	(45,548)	15,255
Amortization of intangible assets	10,909	11,113	2,942
Amortization of right of use lease asset	12,290	22,850	0
Decrease in operating lease liability	(12,170)	(12,507)	0
Income from mortgage banking activities, net	(30,201)	(11,053)	(6,286)
Gain on sale of securities, net	(9,076)	(333)	(21)
(Gain) loss on sale of other real estate owned and valuation adjustments, net	(25)	125	100
Stock-based compensation expense	2,677	3,608	2,292
Unrealized gains on equity investments, net	(761)	(26,175)	(20,745)
Realized gain on sale of equity investment, net	(22,052)	0	(3,757)
Deferred income tax (benefit) expense	(32,848)	7,074	3,378
(Increase) decrease in accrued interest receivable	(6,241)	1,406	(2,596)
Increase in other assets	(18,339)	(4,676)	(6,297)
Origination of loans held-for-sale	(942,188)	(479,289)	(351,108)
Proceeds from sales of loans held-for-sale	824,134	406,012	352,002
(Decrease) increase in accrued interest payable	(1,653)	1,203	863
Increase (decrease) in other liabilities	24,675	30,922	(2,931)
Increase in value of bank-owned life insurance	(1,757)	(806)	(158)
Increase in capitalized interest, net	(3,572)	(3,390)	(3,601)
Net cash provided by operating activities	15,142	89,866	135,574
Investing activities:
Purchases of investment securities held to maturity	(6,307)	0	0
Repayments, maturities and calls of investment securities held to maturity	27,085	16,170	9,245
Sale of investment securities available-for-sale	305,812	618,194	7,012
Purchases of investment securities available-for-sale	(1,454,699)	(958,259)	(498,465)
Repayments of investment securities available-for-sale	606,156	269,697	112,665
Proceeds from bank-owned life insurance surrender	0	59,710	96,429
Net proceeds from sale of Visa Class B shares	85,850	0	0
Cash Acquired from Acquisition	0	76,072	0
Net (increase) decrease in loans and leases	(449,091)	201,934	(101,174)
Purchases of Visa Class B shares	0	0	(1,568)
Sale of Visa Class B shares	0	0	6,186
Purchases of FHLB stock	(145,400)	(394,428)	(169,613)
Redemption of FHLB stock	160,726	415,771	181,638
Sales of assets acquired through foreclosure, net	2,014	3,089	3,037
Sale of premise and equipment	69	71	198
Investment in premises and equipment, net	(7,159)	(14,198)	(5,500)
Net cash (used in) provided by investing activities	(874,944)	293,823	(359,910)
Financing activities:
Net increase in demand and saving deposits	2,501,442	69,761	393,827
(Decrease) increase in time deposits	(197,765)	(55,400)	43,871
Decrease in brokered deposits	(29,474)	(156,396)	(31,712)
Receipts from FHLB advances	5,047,424	32,320,456	83,721,532
Repayments of FHLB advances	(5,153,476)	(32,536,246)	(84,103,068)
Receipts from federal funds purchased	8,030,475	32,252,775	21,239,675
Repayments of federal funds purchased	(8,225,475)	(32,215,750)	(21,109,700)
Contribution from noncontrolling shareholders	23	0	0
Cash dividend	(24,369)	(22,463)	(13,249)
Issuance of common stock and exercise of common stock options	2,032	7,755	11,253
Issuance of senior debt, net of costs	147,780	0	0
Repurchase of common shares	(155,832)	(97,186)	(31,202)
Net cash provided by (used in) financing activities	1,942,785	(432,694)	121,227
Increase (decrease) in cash, cash equivalents, and restricted cash	1,082,983	(49,005)	(103,109)
Cash, cash equivalents, and restricted cash at beginning of period	571,752	620,757	723,866
Cash, cash equivalents, and restricted cash at end of period	1,654,735	571,752	620,757
Supplemental disclosure of cash flow information:
Cash paid for interest during the period	50,103	74,942	45,636
Cash paid for income taxes, net	72,756	33,843	33,316
Non-cash information:
Loans transferred to other real estate owned	2,674	2,541	3,302
Loans transferred to portfolio from held-for-sale at fair value	34,517	24,862	9,553
Fair value of assets acquired, net of cash received	0	5,032,156	0
Fair value of liabilities assumed	0	5,108,228	0
Allowance for credit losses on held-to-maturity debt securities	6
Allowance for credit loss	228,804	47,576	$ 39,539
Retained earnings	977,414	917,377
Accounting standards update extensible list			us-gaap:AccountingStandardsUpdate201601Member
Accounting Standards Update 2016-02
Non-cash information:
Right of use asset	0	121,288
Lease liability	$ 0	$ (132,346)
Accounting standards update extensible list	us-gaap:AccountingStandardsUpdate201602Member
ASC 326
Non-cash information:
Accounting standards update extensible list	us-gaap:AccountingStandardsUpdate201613Member