Consolidated Statements of Cash Flows - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Activities
Net income		$ 266,400	$ 210,544	$ 181,878
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for credit losses		39,765	57	9,953
Net amortization of debt securities		16,893	12,985	13,095
Net accretion of purchase accounting adjustments and deferred loan fees and costs		(57,627)	(3,712)	(3,963)
Amortization of debt modification costs		0	4,630	1,649
Origination of loans held for sale		(2,070,843)	(983,988)	(841,451)
Proceeds from loans held for sale		2,093,549	985,345	896,145
Gain on sale of loans		(99,450)	(34,064)	(27,134)
(Gain) loss on sale of debt securities		(1,139)	(14,415)	1,113
Bank-owned life insurance income, net		(2,724)	(2,245)	(2,234)
Stock-based compensation, net of tax benefits		3,629	7,475	3,122
Depreciation and amortization of premises and equipment		20,420	18,592	16,019
Loss on sale and write-downs of other real estate owned, net		139	73	2,130
Deferred tax (benefit) expense	[1]	(6,863)	(356)	6,861
Core deposit intangible amortization		10,370	8,485	6,270
Amortization of investments in variable interest entities		11,282	9,700	7,639
Net (increase) decrease in accrued interest receivable		(17,663)	1,899	(2,741)
Net (increase) decrease in other assets		(20,926)	5,078	348
Net (decrease) increase in accrued interest payable		(1,507)	312	357
Net increase in other liabilities		5,840	254	11,655
Net cash provided by operating activities		189,545	226,649	280,711
Investing Activities
Sales of available-for-sale debt securities		0	712,113	226,842
Maturities, prepayments and calls of available-for-sale debt securities		758,879	711,838	357,876
Purchases of available-for-sale debt securities		(3,254,912)	(1,224,231)	(820,333)
Maturities, prepayments and calls of held-to-maturity debt securities		32,735	58,750	76,832
Principal collected on loans		4,732,941	3,250,220	2,691,953
Loan originations		(5,864,038)	(3,623,548)	(3,460,227)
Net additions to premises and equipment		(11,717)	(16,398)	(18,637)
Proceeds from sale of other real estate owned		5,572	4,670	9,385
Proceeds from redemption of non-marketable equity securities		76,618	118,516	87,221
Purchases of non-marketable equity securities		(71,399)	(97,597)	(87,975)
Proceeds from bank-owned life insurance		0	0	1,331
Investments in variable interest entities		(12,088)	(16,348)	(37,956)
Net cash received from acquisitions		43,713	79,333	101,268
Net cash used in investing activities		(3,563,696)	(42,682)	(872,420)
Financing Activities
Net increase in deposits		3,418,199	285,856	599,037
Net increase in securities sold under agreements to repurchase		427,510	172,264	4,398
Net (decrease) increase in short-term Federal Home Loan Bank advances		(30,000)	(255,000)	85,000
Proceeds from long-term Federal Home Loan Bank advances		30,000	0	0
Repayments of long-term Federal Home Loan Bank advances		(38,589)	(151,160)	(1,198)
Net increase (decrease) in other borrowed funds		564	14,109	(5,059)
Cash dividends paid		(131,263)	(124,468)	(85,493)
Tax withholding payments for stock-based compensation		(1,082)	(1,293)	(1,214)
Proceeds from stock option exercises		993	2,896	24
Net cash provided by (used in) financing activities		3,676,332	(56,796)	595,495
Net increase in cash, cash equivalents and restricted cash		302,181	127,171	3,786
Cash, cash equivalents and restricted cash at beginning of period		330,961	203,790	200,004
Cash, cash equivalents and restricted cash at end of period		633,142	330,961	203,790
Supplemental Disclosure of Cash Flow Information
Cash paid during the period for interest		28,822	42,461	35,174
Cash paid during the period for income taxes		63,021	36,817	26,489
Supplemental Disclosure of Non-Cash Investing Activities
Transfer of debt securities from held-to-maturity to available-for-sale		0	0	270,331
Sale and refinancing of other real estate owned		215	7	406
Transfer of loans to other real estate owned		2,076	2,349	4,924
Right-of-use assets obtained in exchange for operating lease liabilities		7,406	9,948	0
Dividends declared during the period but not paid		14,572	18,686	25,726
Fair value of common stock shares issued		112,133	316,538	250,807
Cash consideration		13,721	16,424	16,265
Effective settlement of pre-existing receivable		0	0	10,054
Fair value of assets acquired		745,420	1,357,099	1,660,882
Liabilities assumed		$ 619,566	$ 1,024,137	$ 1,383,756

[1] Includes tax benefit of operating loss carryforwards of $315,000, $317,000 and $443,000 for the years ended December 31, 2020, 2019, and 2018, respectively.