Consolidated Statements of Cash Flows - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Cash Flows From Operating Activities
Net income	$ 25,019,000	$ 21,991,000	$ 71,163,000	$ 65,394,000
Reconciliation of net income to net cash provided by operating activities:
Provision (reversal) for loan losses	(1,105,000)	87,000	(913,000)	(4,282,000)	$ (3,589,000)
Net security premium amortization			1,827,000	2,184,000
Loan discount accretion			(4,473,000)	(5,982,000)
Other purchase accounting accretion and amortization, net			(16,000)	(165,000)
Foreclosed property (gains) losses and write-downs, net	273,000	192,000	899,000	579,000
Gains on securities available for sale			(97,000)	0
Other losses (gains)			331,000	(811,000)
Increase in net deferred loan costs			(261,000)	(1,475,000)
Depreciation of premises and equipment			4,326,000	4,420,000
Amortization of operating lease right-of-use assets			1,372,000	0
Repayments of lease obligations			(1,250,000)	0
Stock-based compensation expense			1,748,000	1,201,000
Amortization of intangible assets	1,163,000	1,452,000	3,737,000	4,518,000
Amortization of SBA servicing assets			975,000	555,000
Fees/gains from sale of presold mortgages and SBA loans			(9,725,000)	(11,004,000)
Origination of presold mortgage loans in process of settlement			(108,723,000)	(97,081,000)
Proceeds from sales of presold mortgage loans in process of settlement			99,606,000	105,506,000
Origination of SBA loans for sale			(125,982,000)	(162,782,000)
Proceeds from sales of SBA loans			101,349,000	130,460,000
Increase in accrued interest receivable			(293,000)	(888,000)
Increase in other assets			(4,061,000)	(893,000)
Increase in accrued interest payable			193,000	681,000
Increase (decrease) in other liabilities			1,690,000	(6,448,000)
Net cash provided by operating activities			33,422,000	23,687,000
Cash Flows From Investing Activities
Purchases of securities available for sale			(339,030,000)	(48,975,000)
Proceeds from maturities/issuer calls of securities available for sale			114,003,000	27,609,000
Proceeds from maturities/issuer calls of securities held to maturity			26,316,000	12,841,000
Proceeds from sales of securities available for sale	39,797,000		39,797,000	0
Redemptions (purchases) of FRB and FHLB stock, net			4,088,000
Redemptions (purchases) of FRB and FHLB stock, net				(6,129,000)
Net increase in loans			(116,664,000)	(103,091,000)
Proceeds from sales of foreclosed properties			4,628,000	6,829,000
Purchases of premises and equipment			(2,714,000)	(6,656,000)
Proceeds from sales of premises and equipment			1,148,000	2,739,000
Net cash used by investing activities			(268,428,000)	(114,833,000)
Cash Flows From Financing Activities
Net increase in deposits			216,195,000	121,719,000
Net decrease in borrowings			(106,089,000)	(1,086,000)
Cash dividends paid – common stock			(10,108,000)	(8,308,000)
Repurchases of common stock			(10,000,000)	0
Proceeds from stock option exercises	0	0	129,000	324,000
Stock withheld for payment of taxes			(558,000)	(264,000)
Net cash provided by financing activities			89,569,000	112,385,000
(Decrease) increase in cash and cash equivalents			(145,437,000)	21,239,000
Cash and cash equivalents, beginning of period			462,898,000	489,490,000	489,490,000
Cash and cash equivalents, end of period	$ 317,461,000	$ 510,729,000	317,461,000	510,729,000	$ 462,898,000
Supplemental Disclosures of Cash Flow Information:
Cash paid during the period for interest			25,397,000	15,750,000
Cash paid during the period for income taxes			20,106,000	17,333,000
Non-cash transactions:
Unrealized gain (loss) on securities available for sale, net of taxes			15,137,000	(7,839,000)
Foreclosed loans transferred to other real estate			2,676,000	$ 2,159,000
Initial recognition of operating lease right-of-use assets			19,459,000
Initial recognition of operating lease liabilities			$ 19,459,000