Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flow from operating activities
Net income	$ 64,960,000	$ 59,845,000	$ 50,254,000
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	12,285,000	12,100,000	8,490,000
Provision for loan losses	1,500,000	10,403,000	10,200,000
Deferred income tax expense	10,220,000	2,840,000	2,557,000
Loss on write-down of investments in securities available for sale	405,000	(191,000)	(230,000)
Net loss on fixed assets	221,000	469,000	560,000
Gain on extinguishment of debt	0	0	(763,000)
Loss on termination of derivatives	0	1,122,000	0
Net loss on other real estate owned and foreclosed assets	1,152,000	723,000	606,000
Realized gain on sale leaseback transaction	(1,034,000)	(1,034,000)	(1,034,000)
Stock based compensation	2,490,000	2,712,000	2,462,000
Excess tax benefit related to equity award activity	(1,042,000)	(704,000)	(503,000)
Increase in cash surrender value of life insurance policies	(3,692,000)	(3,128,000)	(3,229,000)
Gain on life insurance benefits	0	(1,964,000)	(227,000)
Change in fair value on loans held for sale	22,000	(18,000)
Net change in:
Securities - trading	(356,000)	0	0
Loans held for sale	876,000	2,012,000	39,305,000
Other assets	3,812,000	(2,191,000)	48,903,000
Other liabilities	(2,276,000)	7,309,000	(16,016,000)
Total adjustments	24,583,000	30,460,000	91,081,000
Net cash provided by operating activities	89,543,000	90,305,000	141,335,000
Cash flows used in investing activities
Proceeds from sales of securities available for sale	14,199,000	5,438,000	3,506,000
Proceeds from maturities and principal repayments of securities available for sale	78,497,000	47,720,000	81,727,000
Purchases of securities available for sale	(73,064,000)	(37,047,000)	(47,975,000)
Proceeds from maturities and principal repayments of securities held to maturity	60,168,000	44,710,000	49,165,000
Purchases of securities held to maturity	(162,021,000)	(69,544,000)	(222,027,000)
Redemption of Federal Home Loan Bank stock	23,054,000	6,693,000	3,093,000
Investments in low income housing projects	(15,055,000)	(16,452,000)	0
Purchases of life insurance policies	(162,000)	(10,161,000)	(267,000)
Proceeds from life insurance policies	0	6,310,000	0
Net increase in loans	(114,550,000)	(266,961,000)	(84,264,000)
Cash provided by (used in) business combinations	(13,448,000)	0	10,520,000
Purchases of bank premises and equipment	(10,488,000)	(7,678,000)	(9,293,000)
Proceeds from the sale of bank premises and equipment	1,233,000	1,219,000	29,000
Payments on early termination of hedging relationship		(1,122,000)
Proceeds from the sale of other real estate owned and foreclosed assets	7,667,000	7,458,000	9,731,000
Net payments relating to other real estate owned and foreclosed assets	1,571,000	3,255,000	2,541,000
Net cash used in investing activities	(205,541,000)	(292,672,000)	(208,596,000)
Cash flows provided by financing activities
Net decrease in time deposits	(80,726,000)	(94,008,000)	(79,136,000)
Net increase in other deposits	428,713,000	318,056,000	300,000,000
Net repayments of short-term Federal Home Loan Bank borrowings	(10,000,000)	(65,000,000)	(50,000,000)
Repayments of long-term Federal Home Loan Bank borrowings	(9,000,000)	(5,000,000)	(79,946,000)
Net decrease in customer repurchase agreements	(13,932,000)	(1,398,000)	(4,071,000)
Increase (Decrease) in Payables under Repurchase Agreements	(50,000,000)	0	0
Net decrease in other short term borrowings		(5,000,000)	(7,000,000)
Repayments of Subordinated Debt	(30,000,000)	35,000,000	0
Net proceeds from exercise of stock options	1,367,000	2,333,000	2,475,000
Restricted stock awards issued, net of awards surrendered	(657,000)	(641,000)	(669,000)
Excess tax benefit from stock based compensation	1,042,000	704,000	503,000
Tax benefit from deferred compensation distribution	179,000	138,000	109,000
Proceeds from shares issued under the direct stock purchase plan	2,695,000	1,555,000	969,000
Common dividends paid	(26,172,000)	(22,443,000)	(15,122,000)
Net cash provided by financing activities	213,509,000	164,296,000	68,112,000
Net increase (decrease) in cash and cash equivalents	97,511,000	(38,071,000)	851,000
Cash and cash equivalents at beginning of year	178,254,000	216,325,000	215,474,000
Cash and cash equivalents at end of period	275,765,000	178,254,000	216,325,000
Supplemental schedule of noncash investing and financing activities
Interest on deposits and borrowings	20,773,000	20,257,000	23,475,000
Income taxes	11,841,000	14,547,000	12,171,000
Transfer of loans to other real estate owned and foreclosed assets	1,522,000	5,248,000	2,869,000
Real Estate Owned, Transfer to Real Estate Owned	142,000
Capital commitment relating to Low Income Housing Project investments, noncash	1,658,000	38,839,000	51,000
In conjunction with the purchase acquisition detailed in note 2 to the consolidated financial statements, assets were acquired and liabilities were assumed as follows
Common stock issued for acquisition	86,415,000	$ 0	29,390,000
Fair value of assets acquired, net of cash acquired	598,376,000		241,395,000
Fair value of liabilities assumed	$ 498,513,000		$ 222,525,000