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, 2010	$ 697,394	$ 580,097	$ 310,271	$ (12,044)	$ (180,930)
Beginning Balances (in shares) at Dec. 31, 2010		68,730,731			(10,665,754)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	33,180		33,180
Other comprehensive income	4,142			4,142
Cash dividends declared :
Common stock at $0.60 per share in 2012 and $0.24 per share in 2011	(13,996)		(13,996)
Excess tax benefit on share-based compensation	156	156
Exercise of stock options, net of shares purchased (in shares)					12,808
Exercise of stock options, net of shares purchased	(11)	(228)			217
Restricted stock awards, net of forfeitures (in shares)					181,655
Restricted stock awards, net of forfeitures	908	(3,974)			(3,066)
Share-based compensation expense	1,805	1,805
Ending Balances at Jun. 30, 2011	721,762	577,856	329,455	(7,902)	(177,647)
Ending Balances (in shares) at Jun. 30, 2011		68,730,731			(10,471,291)
Beginning Balances at Dec. 31, 2011	712,221	579,871	331,351	(21,490)	(177,511)
Beginning Balances (in shares) at Dec. 31, 2011		68,730,731			(10,463,677)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	34,796		34,796
Other comprehensive income	3,318			3,318
Cash dividends declared :
Common stock at $0.60 per share in 2012 and $0.24 per share in 2011	(34,832)		(34,832)
Excess tax benefit on share-based compensation	348	348
Exercise of stock options, net of shares purchased (in shares)					57,604
Exercise of stock options, net of shares purchased	63	(914)			977
Restricted stock awards, net of forfeitures (in shares)					188,735
Restricted stock awards, net of forfeitures	1,068	(4,318)			(3,250)
Share-based compensation expense	1,942	1,942
Ending Balances at Jun. 30, 2012	$ 716,788	$ 576,929	$ 331,315	$ (18,172)	$ (173,284)
Ending Balances (in shares) at Jun. 30, 2012		68,730,731			(10,217,338)