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	13,824		13,824
Other comprehensive income (loss)	(2,798)			(2,798)
Cash dividends declared :
Common stock at $0.79 per share in 2013 and $0.90 per share in 2012	(16,193)		(16,193)
Purchase of common stock, in shares					(249,000)
Purchase of common stock	(3,831)				(3,831)
Excess tax benefit on share-based compensation	73	73
Exercise of stock options, net of shares purchased (in shares)					20,370
Exercise of stock options, net of shares purchased	(136)	(479)			343
Restricted stock awards, net of forfeitures (in shares)					211,318
Restricted stock awards, net of forfeitures	(837)	(4,460)			3,623
Share-based compensation expense	1,087	1,087
Ending Balances at Mar. 31, 2013	701,614	575,514	327,635	(21,475)	(180,060)
Ending Balances (in shares) at Mar. 31, 2013		68,730,731			(10,701,808)
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	15,104		15,104
Other comprehensive income (loss)	3,633			3,633
Cash dividends declared :
Common stock at $0.79 per share in 2013 and $0.90 per share in 2012	(8,624)		(8,624)
Purchase of common stock, in shares					(40,255)
Purchase of common stock	(697)				(697)
Excess tax benefit on share-based compensation	254	254
Exercise of stock options, net of shares purchased (in shares)					33,794
Exercise of stock options, net of shares purchased	(139)	(703)			564
Restricted stock awards, net of forfeitures (in shares)					183,352
Restricted stock awards, net of forfeitures	(1,155)	(4,194)			3,039
Share-based compensation expense	810	810
Ending Balances at Mar. 31, 2014	$ 691,347	$ 573,243	$ 330,672	$ (27,648)	$ (184,920)
Ending Balances (in shares) at Mar. 31, 2014		68,730,731			(11,020,794)