CONSOLIDATED STATEMENT OF CHANGES IN SHAREHOLDERS' EQUITY (Unaudited) - 3 months ended Mar. 31, 2017 - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]	Treasury Stock [Member]	Total
Balance at Dec. 31, 2016	$ 44,950	$ 545,775	$ 614,692	$ 7,843	$ (15,160)	$ 1,198,100
Balance (in shares) at Dec. 31, 2016	44,437,415
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income			26,257			26,257
Other comprehensive income, net of tax				2,511		2,511
Cash dividends declared:
Common, $0.32 per share			(14,691)			(14,691)
Common stock issued under employee stock plan	$ 158	1,651				1,809
Common stock issued under employee stock plan (in shares)	157,801
Stock-based compensation		1,410				1,410
Stock issued for acquisition	$ 1,323	77,160				78,483
Stock issued for acquisition (in shares)	1,322,364
Treasury stock issued to benefit plan		1,019			1,132	2,151
Treasury stock issued to benefit plan (in shares)	38,302
Balance at Mar. 31, 2017	$ 46,431	$ 627,015	$ 626,258	$ 10,354	$ (14,028)	$ 1,296,030
Balance (in shares) at Mar. 31, 2017	45,955,882