CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Retained earnings	Accumulated other comprehensive income (loss)	Treasury stock
Beginning Balances (in shares) at Dec. 31, 2016		68,730,731			(6,751,179)
Beginning Balances at Dec. 31, 2016	$ 865,224	$ 570,382	$ 437,188	$ (28,443)	$ (113,903)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	47,150		47,150
Other comprehensive income (loss)	6,221			6,221
Cash dividends declared :
Common stock at $0.38 per share in 2018 and $0.34 per share in 2017	(21,088)		(21,088)
Stock Issued During Period, Shares, Other					1,484
Adjustments to Additional Paid in Capital, Other	0	(25)			$ 25
Exercise of stock options, net of shares purchased (in shares)					39,062
Exercise of stock options, net of shares purchased	198	(462)			$ 660
Restricted stock awards, net of forfeitures (in shares)					120,973
Restricted stock awards, net of forfeitures	(2,554)	(3,559)			$ 1,005
Share-based compensation expense	2,966	$ 2,966
Ending Balances (in shares) at Jun. 30, 2017		68,730,731			(6,589,660)
Ending Balances at Jun. 30, 2017	898,117	$ 569,302	463,250	(22,222)	$ (112,213)
Beginning Balances (in shares) at Dec. 31, 2017		68,730,731			(6,661,644)
Beginning Balances at Dec. 31, 2017	930,664	$ 573,109	491,847	(20,390)	$ (113,902)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	66,924		66,924
Reclassification from AOCI, Current Period, Tax	0		4,942	(4,942)
Other comprehensive income (loss)	(17,676)			(17,676)
Cash dividends declared :
Common stock at $0.38 per share in 2018 and $0.34 per share in 2017	(30,394)		(30,394)
Stock Issued During Period, Shares, New Issues		35,551,063
Stock Issued During Period, Value, Acquisitions	1,045,876	$ 1,045,876
Stock Options and Warrants Acquired And Converted Pursuant To Acquisition	16,037	16,037
Stock Issued During Period, Shares, Other					53,907
Adjustments to Additional Paid in Capital, Other	0	(922)			$ 922
Exercise of stock options, net of shares purchased (in shares)					31,554
Exercise of stock options, net of shares purchased	267	(275)			$ 542
Restricted stock awards, net of forfeitures (in shares)					199,286
Restricted stock awards, net of forfeitures	(2,207)	(4,699)			$ 2,492
Share-based compensation expense	3,446	$ 3,446
Ending Balances (in shares) at Jun. 30, 2018		104,281,794			(6,376,897)
Ending Balances at Jun. 30, 2018	$ 2,012,937	$ 1,632,572	$ 533,319	$ (43,008)	$ (109,946)