Consolidated Statements of Cash Flows - USD ($)		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Activities
Net income		$ 210,544,000	$ 181,878,000	$ 116,377,000
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses		57,000	9,953,000	10,824,000
Net amortization of debt securities		12,985,000	13,095,000	20,026,000
Net accretion of purchase accounting adjustments		(3,712,000)	(3,963,000)	(5,131,000)
Amortization of debt modification costs		4,630,000	1,649,000	471,000
Origination of loans held for sale		(983,988,000)	(841,451,000)	(889,212,000)
Proceeds from loans held for sale		985,345,000	896,145,000	984,506,000
Gain on sale of loans		(34,064,000)	(27,134,000)	(30,439,000)
(Gain) loss on sale of debt securities		(14,415,000)	1,113,000	660,000
Bank-owned life insurance income, net		(2,245,000)	(2,234,000)	(1,395,000)
Stock-based compensation, net of tax benefits		7,475,000	3,122,000	2,952,000
Depreciation and amortization of premises and equipment		18,592,000	16,019,000	14,758,000
Loss (gain) on sale and write-downs of other real estate owned, net		73,000	2,130,000	(1,641,000)
Deferred tax (benefit) expense	[1]	(356,000)	6,861,000	25,887,000
Core deposit intangible amortization		8,485,000	6,270,000	2,494,000
Amortization of investments in variable interest entities		9,700,000	7,639,000	4,692,000
Net decrease (increase) in accrued interest receivable		1,899,000	(2,741,000)	2,466,000
Net decrease in other assets		5,078,000	348,000	1,139,000
Net increase (decrease) in accrued interest payable		312,000	357,000	(135,000)
Net increase (decrease) in other liabilities		254,000	11,655,000	(4,558,000)
Net cash provided by operating activities		226,649,000	280,711,000	254,741,000
Investing Activities
Sales of available-for-sale debt securities		712,113,000	226,842,000	247,748,000
Maturities, prepayments and calls of available-for-sale debt securities		711,838,000	357,876,000	446,695,000
Purchases of available-for-sale debt securities		(1,224,231,000)	(820,333,000)	(36,239,000)
Maturities, prepayments and calls of held-to-maturity debt securities		58,750,000	76,832,000	25,187,000
Principal collected on loans		3,250,220,000	2,691,953,000	2,099,292,000
Loan originations		(3,623,548,000)	(3,460,227,000)	(2,740,281,000)
Net additions to premises and equipment		(16,398,000)	(18,637,000)	(10,128,000)
Proceeds from sale of other real estate owned		4,670,000	9,385,000	12,335,000
Proceeds from redemption of non-marketable equity securities		118,516,000	87,221,000	68,610,000
Purchases of non-marketable equity securities		(97,597,000)	(87,975,000)	(71,396,000)
Proceeds from bank-owned life insurance		0	1,331,000	437,000
Investments in variable interest entities		(16,348,000)	(37,956,000)	(14,514,000)
Net cash received from (paid in) acquisitions		79,333,000	101,268,000	(4,091,000)
Net cash (used in) provided by investing activities		(42,682,000)	(872,420,000)	23,655,000
Financing Activities
Net increase in deposits		285,856,000	599,037,000	(89,397,000)
Net increase in securities sold under agreements to repurchase		172,264,000	4,398,000	(111,077,000)
Net (decrease) increase in short-term Federal Home Loan Bank advances		(255,000,000)	85,000,000	137,200,000
Proceeds from long-term Federal Home Loan Bank advances		0	0	150,000,000
Repayments of long-term Federal Home Loan Bank advances		(151,160,000)	(1,198,000)	(208,192,000)
Net increase (decrease) in other borrowed funds		14,109,000	(5,059,000)	3,784,000
Cash dividends paid		(124,468,000)	(85,493,000)	(111,720,000)
Tax withholding payments for stock-based compensation		(1,293,000)	(1,214,000)	(1,531,000)
Proceeds from stock option exercises		2,896,000	24,000	0
Net cash (used in) provided by financing activities		(56,796,000)	595,495,000	(230,933,000)
Net increase in cash, cash equivalents and restricted cash		127,171,000	3,786,000	47,463,000
Cash, cash equivalents and restricted cash at beginning of period		203,790,000	200,004,000	152,541,000
Cash, cash equivalents and restricted cash at end of period		330,961,000	203,790,000	200,004,000
Supplemental Disclosure of Cash Flow Information
Cash paid during the period for interest		42,461,000	35,174,000	30,000,000
Cash paid during the period for income taxes		36,817,000	26,489,000	40,219,000
Supplemental Disclosure of Non-Cash Investing Activities
Transfer of debt securities from held-to-maturity to available-for-sale		0	270,331,000	0
Sale and refinancing of other real estate owned		7,000	406,000	553,000
Transfer of loans to other real estate owned		2,349,000	4,924,000	4,466,000
Right-of-use assets obtained in exchange for operating lease liabilities		9,948,000	0	0
Dividends declared during the period but not paid		18,686,000	25,726,000	265,000
Fair value of common stock shares issued		316,538,000	250,807,000	46,673,000
Cash consideration		16,424,000	16,265,000	17,342,000
Effective settlement of pre-existing receivable		0	10,054,000	0
Fair value of assets acquired		1,190,267,000	1,660,882,000	355,230,000
Liabilities assumed		$ 1,024,137,000	$ 1,383,756,000	$ 321,824,000

[1] Includes tax benefit of operating loss carryforwards of $317,000, $443,000 and $644,000 for the years ended December 31, 2019, 2018, and 2017, respectively.