CONSOLIDATED STATEMENT OF CHANGES IN SHAREHOLDERS' EQUITY (Unaudited) - 6 months ended Jun. 30, 2017 - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]	Treasury Stock [Member]	Deferred Compensation Arrangements [Member]	Total
Balance at Dec. 31, 2016	$ 44,950	$ 545,775	$ 614,692	$ 7,843	$ (15,160)	$ 0	$ 1,198,100
Balance (in shares) at Dec. 31, 2016	44,437,415
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income			43,448				43,448
Other comprehensive income, net of tax				9,799			9,799
Cash dividends declared:
Common, $0.64 per share			(30,912)				(30,912)
Common stock issued under employee stock plan	$ 192	2,637					2,829
Common stock issued under employee stock plan (in shares)	191,590
Stock-based compensation		2,730					2,730
Stock issued for acquisitions	$ 6,006	334,731					340,737
Stock issued for acquisitions (in shares)	6,006,301
Deferred compensation arrangements acquired					(10,022)	10,022	0
Deferred compensation arrangements acquired (in shares)	(179,003)
Treasury stock issued to benefit plans, net		1,432			1,659	3,078	6,169
Treasury stock issued to benefit plans, net (in shares)	55,632
Balance at Jun. 30, 2017	$ 51,148	$ 887,305	$ 627,228	$ 17,642	$ (23,523)	$ 13,100	$ 1,572,900
Balance (in shares) at Jun. 30, 2017	50,511,935