Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities
Net income	$ 121,021	$ 112,566	$ 82,151
Adjustments to reconcile net income to net cash provided by operating activities
Provision for loan losses	25,412	28,828	30,988
Depreciation and amortization of premises and equipment	9,497	9,280	9,056
Net amortization on securities	3,375	4,007	4,786
Amortization of intangible assets	3,579	4,042	3,960
Amortization of operating lease right-of-use assets	7,239	0	0
Excess tax benefit on stock-based compensation	(409)	(543)	(1,769)
Stock-based compensation expense	4,210	3,936	3,644
Bank owned life insurance income	(5,355)	(5,091)	(5,175)
Trading security purchases	0	0	(1,586)
Net unrealized losses on trading securities	0	0	(623)
Proceeds from sale of loans held for sale	175,829	102,547	111,284
Originations of loans held for sale	(181,261)	(108,070)	(111,206)
Net gains on sale of loans held for sale	(786)	(286)	(349)
Net security (gains) losses	(4,213)	6,341	(1,867)
Net losses (gains) on sales and write-down of other real estate owned	227	(230)	(221)
Gain on sale of equity investment	0	0	(818)
Impairment write-down of equity security	0	0	1,312
Impairment write-down of goodwill and intangible assets	0	0	1,530
Re-evaluation of deferred tax amounts from Tax Act	0	0	4,407
Net change in other assets and other liabilities	(4,902)	(9,554)	7,400
Net cash provided by operating activities	153,463	147,773	136,904
Investing activities
Net cash used in acquisitions	0	(7,884)	(4,000)
Securities available for sale:
Proceeds from maturities, calls and principal paydowns	273,578	259,446	290,613
Proceeds from sales	26,203	101,315	14,788
Purchases	(252,963)	(132,448)	(233,804)
Securities held to maturity:
Proceeds from maturities, calls and principal paydowns	223,733	100,738	103,759
Proceeds from sales	0	0	764
Purchases	(70,660)	(400,602)	(60,706)
Equity securities:
Proceeds from sales	3,966	3,318	0
Purchases	(93)	(2)	0
Other:
Net increase in loans	(272,698)	(331,166)	(419,114)
Proceeds from Federal Home Loan Bank stock redemption	182,752	246,844	248,887
Purchases of Federal Reserve and Federal Home Loan Bank stock	(174,143)	(253,367)	(248,560)
Proceeds from settlement of bank owned life insurance	1,086	0	799
Purchases of premises and equipment, net	(6,647)	(7,402)	(6,691)
Proceeds from sale of equity investment	0	0	818
Proceeds from sales of other real estate owned	1,543	3,591	7,254
Net cash (used in) provided by investing activities	(64,343)	(417,619)	(305,193)
Financing activities
Net increase in deposits	219,609	197,575	196,948
Net (decrease) increase in short-term borrowings	(216,421)	152,573	37,419
Proceeds from issuance of long-term debt	10,598	25,000	25,000
Repayments of long-term debt	(20,111)	(40,145)	(40,218)
Proceeds from the issuance of shares to employee and other stock plans	725	1,296	3,309
Cash paid by employer for tax-withholdings on stock issuance	(1,622)	(1,893)	(3,582)
Cash dividends	(46,010)	(43,269)	(40,104)
Net cash (used in) provided by financing activities	(53,232)	291,137	178,772
Net increase (decrease) in cash and cash equivalents	35,888	21,291	10,483
Cash and cash equivalents at beginning of year	180,955	159,664	149,181
Cash and cash equivalents at end of year	216,843	180,955	159,664
Cash paid during the period for:
Interest expense	55,908	36,691	25,887
Income taxes paid	28,374	31,898	33,675
Noncash investing activities:
Loans transferred to other real estate owned	787	1,273	5,981
Acquisitions:
Fair value of assets acquired	$ 0	$ 6,274	$ 3,096