CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock	Retained earnings	Accumulated other comprehensive income (loss)	Treasury stock
Beginning Balances at Dec. 31, 2012	$ 710,425	$ 579,293	$ 330,004	$ (18,677)	$ (180,195)
Beginning Balances (in shares) at Dec. 31, 2012		68,730,731			(10,684,496)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	29,653		29,653
Other comprehensive income (loss)	(6,968)			(6,968)
Cash dividends declared :
Common stock at $0.30 per share in 2014 and $0.52 per share in 2013	(30,024)		(30,024)
Purchase of common stock, in shares					(540,400)
Purchase of common stock	(8,339)				(8,339)
Excess tax benefit on share-based compensation	30	30
Exercise of stock options, net of shares purchased (in shares)					21,526
Exercise of stock options, net of shares purchased	(141)	(503)			362
Restricted stock awards, net of forfeitures (in shares)					170,983
Restricted stock awards, net of forfeitures	(1,321)	(4,316)			2,995
Share-based compensation expense	2,137	2,137
Ending Balances at Jun. 30, 2013	695,452	576,641	329,633	(25,645)	(185,177)
Ending Balances (in shares) at Jun. 30, 2013		68,730,731			(11,032,387)
Beginning Balances at Dec. 31, 2013	682,161	577,076	324,192	(31,281)	(187,826)
Beginning Balances (in shares) at Dec. 31, 2013		68,730,731			(11,197,685)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	31,057		31,057
Other comprehensive income (loss)	9,712			9,712
Cash dividends declared :
Common stock at $0.30 per share in 2014 and $0.52 per share in 2013	(17,278)		(17,278)
Purchase of common stock, in shares					(40,255)
Purchase of common stock	(697)				(697)
Excess tax benefit on share-based compensation	278	278
Exercise of stock options, net of shares purchased (in shares)					34,853
Exercise of stock options, net of shares purchased	(146)	(728)			582
Restricted stock awards, net of forfeitures (in shares)					190,673
Restricted stock awards, net of forfeitures	(1,173)	(4,337)			3,164
Share-based compensation expense	1,917	1,917
Ending Balances at Jun. 30, 2014	$ 705,831	$ 574,206	$ 337,971	$ (21,569)	$ (184,777)
Ending Balances (in shares) at Jun. 30, 2014		68,730,731			(11,012,414)