Consolidated Statements of Cash Flows	12 Months Ended
	Dec. 31, 2018 USD ($)		Dec. 31, 2017 USD ($)		Dec. 31, 2016 USD ($)
Operating Activities
Net income	$ 181,878,000		$ 116,377,000		$ 121,131,000
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses	9,953,000		10,824,000		2,333,000
Net amortization of debt securities	13,095,000		20,026,000		26,210,000
Net accretion of purchase accounting adjustments	(3,963,000)		(5,131,000)		(2,252,000)
Amortization of debt modification costs	1,649,000		471,000		0
Origination of loans held for sale	(841,451,000)		(889,212,000)		(1,098,864,000)
Proceeds from loans held for sale	896,145,000		984,506,000		1,155,186,000
Gain on sale of loans	(27,134,000)		(30,439,000)		(33,606,000)
Loss on sale of debt securities	1,113,000		660,000		1,463,000
Bank-owned life insurance income, net	(2,234,000)		(1,395,000)		(1,142,000)
Stock-based compensation expense, net of tax benefits	3,122,000		2,952,000		1,844,000
Depreciation of premises and equipment	16,019,000		14,758,000		15,294,000
Loss (gain) on sale and write-downs of other real estate owned, net	2,130,000		(1,641,000)		1,217,000
Deferred tax expense (benefit)	6,861,000	[1]	25,887,000	[1]	(82,000)	[1]
Core deposit intangible amortization	6,270,000		2,494,000		2,970,000
Amortization of investments in variable interest entities	7,639,000		4,692,000		2,578,000
Net (increase) decrease in accrued interest receivable	(2,741,000)		2,466,000		(1,144,000)
Net decrease in other assets	348,000		1,139,000		6,621,000
Net increase (decrease) in accrued interest payable	357,000		(135,000)		60,000
Net increase (decrease) in other liabilities	11,655,000		(4,558,000)		(6,730,000)
Net cash provided by operating activities	280,711,000		254,741,000		193,087,000
Investing Activities
Sales of available-for-sale debt securities	226,842,000		247,748,000		62,817,000
Maturities, prepayments and calls of available-for-sale debt securities	357,876,000		446,695,000		662,003,000
Purchases of available-for-sale debt securities	(820,333,000)		(36,239,000)		(585,064,000)
Maturities, prepayments and calls of held-to-maturity debt securities	76,832,000		25,187,000		25,405,000
Purchases of held-to-maturity debt securities	0		0		(1,222,000)
Principal collected on loans	2,691,953,000		2,099,292,000		1,781,534,000
Loan originations	(3,460,227,000)		(2,740,281,000)		(2,375,136,000)
Net additions to premises and equipment	(18,637,000)		(10,128,000)		(8,306,000)
Proceeds from sale of other real estate owned	9,385,000		12,335,000		10,145,000
Proceeds from redemption of non-marketable equity securities	87,221,000		68,610,000		73,611,000
Purchases of non-marketable equity securities	(87,975,000)		(71,396,000)		(67,594,000)
Proceeds from bank-owned life insurance	1,331,000		437,000		437,000
Investments in variable interest entities	(37,956,000)		(14,514,000)		(6,644,000)
Net cash received from (paid in) acquisitions	101,268,000		(4,091,000)		6,701,000
Net cash (used in) provided by investing activities	(872,420,000)		23,655,000		(421,313,000)
Financing Activities
Net increase (decrease) in deposits	599,037,000		(89,397,000)		368,006,000
Net increase (decrease) in securities sold under agreements to repurchase	4,398,000		(111,077,000)		50,236,000
Net increase (decrease) in short-term Federal Home Loan Bank advances	85,000,000		137,200,000		(100,000,000)
Proceeds from long-term Federal Home Loan Bank advances	0		150,000,000		0
Repayments of long-term Federal Home Loan Bank advances	(1,198,000)		(208,192,000)		(45,567,000)
Net (decrease) increase in other borrowed funds	(5,059,000)		3,784,000		(521,000)
Cash dividends paid	(85,493,000)		(111,720,000)		(84,040,000)
Tax withholding payments for stock-based compensation	(1,190,000)		(1,531,000)		(600,000)
Net cash provided by (used in) financing activities	595,495,000		(230,933,000)		187,514,000
Net increase (decrease) in cash, cash equivalents and restricted cash	3,786,000		47,463,000		(40,712,000)
Cash, cash equivalents and restricted cash at beginning of period	200,004,000		152,541,000		193,253,000
Cash, cash equivalents and restricted cash at end of period	203,790,000		200,004,000		152,541,000
Supplemental Disclosure of Cash Flow Information
Cash paid during the period for interest	35,174,000		30,000,000		29,576,000
Cash paid during the period for income taxes	26,489,000		40,219,000		36,225,000
Supplemental Disclosure of Non-Cash Investing Activities
Transfer of debt securities from held-to-maturity to available-for-sale	270,331,000		0		0
Sale and refinancing of other real estate owned	406,000		553,000		728,000
Transfer of loans to other real estate owned	4,924,000		4,466,000		5,198,000
Dividends declared but not paid	25,726,000		265,000		23,137,000
Fair value of common stock shares issued	250,807,000		46,673,000		10,465,000
Cash consideration for outstanding shares	16,265,000		17,342,000		3,475,000
Effective settlement of pre-existing receivable	10,054,000		0		0
Fair value of assets acquired	1,660,882,000		355,230,000		69,750,000
Liabilities assumed	$ 1,383,756,000		$ 321,824,000		$ 62,225,000

[1] Includes tax benefit of operating loss carryforwards of $443,000, $644,000 and $571,000 for the years ended December 31, 2018, 2017, and 2016, respectively.