Consolidated Statements of Cash Flow $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 86,439	$ 70,674	$ 66,170
Adjustments to reconcile to net cash provided by operating activities:
Provision for loan losses	8,512	11,519	7,675
Depreciation and amortization	11,791	12,383	11,901
Net amortization of securities premiums and discounts	(148)	128	1,020
Realized securities (gains) losses	(4,060)	59	(9,269)
Gain on sales of loans	(2,921)	(2,825)	(1,968)
Cash receipts from the sale of loans originated for sale	211,569	189,620	171,723
Cash disbursements for loans originated for sale	(205,574)	(182,425)	(174,047)
Deferred income tax provision (benefit)	4,383	(2,048)	(1,903)
Loss/(gain) on other assets	46	(1,252)	(65)
Increase in interest receivable	(3,284)	(1,497)	(991)
Increase/(decrease) in interest payable	366	69	(105)
Amortization of stock-based compensation arrangements	1,180	1,636	1,717
Excess tax benefit from stock-based compensation arrangements	(2,601)
Other, net	(1,173)	(5,500)	6,301
Net cash provided by operating activities	104,525	90,541	78,159
INVESTING ACTIVITIES
Net cash and due from banks paid for acquisitions			(4,007)
Net (increase)/decrease in federal funds sold		(700)	13,256
Purchases of held for investment securities	(220)	(838)	(1,771)
Purchases of available for sale securities	(85,777)	(224,655)	(91,136)
Proceeds from maturities, calls and paydowns of held for investment securities	2,293	5,260	2,103
Proceeds from maturities, calls and paydowns of available for sale securities	79,063	300,345	55,689
Proceeds from sales of available for sale securities	5,412	481	10,850
Net change in loans	(331,362)	(176,594)	(243,976)
Purchases of premises, equipment and computer software	(18,007)	(10,835)	(11,263)
Proceeds from the sale of other real estate owned and other assets	4,038	9,519	4,957
Net cash used in investing activities	(344,560)	(98,017)	(265,298)
FINANCING ACTIVITIES
Net change in deposits	166,988	274,699	(106,422)
Net change in short-term borrowings	400		(3,482)
Issuance of common stock, net	4,844	13,354	4,428
Common stock acquired		(5,523)	(1,654)
Cash dividends paid	(24,783)	(22,770)	(21,449)
Net cash provided by (used in) financing activities	147,449	259,760	(128,579)
Net (decrease)/increase in cash, due from banks and interest-bearing deposits	(92,586)	252,284	(315,718)
Cash, due from banks and interest-bearing deposits at the beginning of the period	1,850,461	1,598,177	1,913,895
Cash, due from banks and interest-bearing deposits at the end of the period	1,757,875	1,850,461	1,598,177
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Cash paid during the period for interest	20,563	14,673	12,255
Cash paid during the period for income taxes	41,058	32,700	33,531
Noncash investing and financing activities:
Unpaid common stock dividends declared	$ 6,693	$ 5,969	$ 5,615