Consolidated Statements of Cash Flows	12 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Cash flow from operating activities
Net income	$ 121,622,000	$ 87,204,000	$ 76,648,000
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	15,994,000	15,681,000	14,354,000
Provision for loan losses	4,775,000	2,950,000	6,075,000
Deferred income tax expense (benefit)	(4,497,000)	9,211,000	(5,000)
Tax Expense related to a change in tax law	0	466,000	0
Equity Securities, FV-NI, Gain (Loss)	1,225,000
Loss on write-down of investments in securities available for sale		(3,000)	26,000
Net (gain) loss on bank premises and equipment	(1,126,000)	(108,000)	114,000
Net loss on other real estate owned and foreclosed assets	112,000	288,000	29,000
Realized gain on sale leaseback transaction	(730,000)	(1,034,000)	(1,034,000)
Stock based compensation	4,225,000	3,333,000	2,965,000
Excess tax benefit related to equity award activity	0	0	(476,000)
Increase in cash surrender value of life insurance policies	(4,060,000)	(4,127,000)	(4,089,000)
Gain Realized on Life Insurance Policies	(1,463,000)	0
Change in Fair Value on Loans Held for Sale	51,000	113,000	(87,000)
Net change in:
Trading assets	(180,000)	(520,000)	(448,000)
Loans held for sale	(1,714,000)	1,258,000	(62,000)
Other assets	503,000	20,022,000	7,627,000
Other liabilities	7,100,000	(3,825,000)	(8,738,000)
Total adjustments	20,215,000	43,705,000	16,251,000
Net cash provided by operating activities	141,837,000	130,909,000	92,899,000
Cash flows used in investing activities
Proceeds from Sale of Debt and Equity Securities, FV-NI, Held-for-investment	5,752,000
Increase (Decrease) in Equity Securities, FV-NI	(6,315,000)	0	0
Proceeds from Sale of Available-for-sale Securities, Equity		0	0
Proceeds from Sale of Debt Securities, Available-for-sale		1,027,000	618,000
Proceeds from maturities and principal repayments of securities available for sale	82,418,000	54,191,000	69,775,000
Payments to Acquire Debt Securities, Available-for-sale	(78,990,000)	(140,885,000)	(69,671,000)
Proceeds from maturities and principal repayments of securities held to maturity	82,355,000	78,757,000	90,991,000
Purchases of securities held to maturity	(195,538,000)	(89,033,000)	(100,198,000)
Net redemption (purchases) of Federal Home Loan Bank stock	(2,376,000)	386,000	5,229,000
Investments in low income housing projects	(3,434,000)	(7,645,000)	(7,626,000)
Purchases of life insurance policies	(164,000)	(164,000)	(163,000)
Proceeds from Life Insurance Policy	2,850,000	0	0
Net increase in loans	(258,633,000)	(204,702,000)	(227,838,000)
Cash Acquired in Excess of Payments to Acquire Business		6,289,000	8,668,000
Net cash acquired (paid) in business combinations	(6,906,000)
Purchases of bank premises and equipment	(11,106,000)	(25,080,000)	(10,395,000)
Proceeds from the sale of bank premises and equipment	2,189,000	6,306,000	345,000
Proceeds from the sale of other real estate owned and foreclosed assets	387,000	3,784,000	1,583,000
Net payments relating to other real estate owned and foreclosed assets	0	0	(204,000)
Net cash used in investing activities	(387,511,000)	(316,769,000)	(238,886,000)
Cash flows provided by financing activities
Net decrease in time deposits	(1,430,000)	(19,509,000)	(104,803,000)
Net increase in other deposits	280,017,000	177,241,000	350,739,000
Net proceeds from (repayments of) short-term Federal Home Loan Bank borrowings	67,046,000		(37,000,000)
Repayments of long-term Federal Home Loan Bank borrowings	(2,475,000)	0	(65,791,000)
Net increase (decrease) in customer repurchase agreements	(21,503,000)	(14,234,000)	42,955,000
Gain (Loss) on Extinguishment of Debt	0	0	(437,000)
Net proceeds from exercise of stock options	184,000	214,000	201,000
Restricted stock awards issued, net of awards surrendered	(1,371,000)	(1,422,000)	(696,000)
Excess tax benefit from stock based compensation			476,000
Tax benefit from deferred compensation distribution			187,000
Proceeds from shares issued under the direct stock purchase plan	2,712,000	1,636,000	2,323,000
Common dividends paid	(40,167,000)	(34,045,000)	(29,711,000)
Net cash provided by financing activities	283,013,000	109,881,000	159,317,000
Net increase (decrease) in cash and cash equivalents	37,339,000	(75,979,000)	13,330,000
Cash and cash equivalents at beginning of year	213,116,000	289,095,000	275,765,000
Cash and cash equivalents at end of period	250,455,000	213,116,000	289,095,000
Supplemental schedule of noncash investing and financing activities
Interest on deposits and borrowings	25,337,000	18,626,000	18,963,000
Income taxes	27,809,000	32,865,000	33,473,000
Transfer of loans to other real estate owned and foreclosed assets		511,000	1,322,000
Capital commitment relating to Low Income Housing Project investments, noncash	2,833,000	20,000	5,180,000
Transfer of customer repurchase agreements to deposits noncash	141,176,000	0	0
In conjunction with the Company's acquisitions, assets were acquired and liabilities were assumed as follows
Common stock issued for acquisition	42,474,000	23,468,000	40,730,000
Fair value of assets acquired, net of cash acquired	362,286,000	179,252,000	266,242,000
Fair value of liabilities assumed	$ 312,906,000	$ 162,073,000	$ 234,180,000