CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $) In Thousands, unless otherwise specified	Total	Common Stock	Shares Held Under Employee Participation Plan	Additional Paid-in Capital	Accumulated Other Comprehensive Income	Accumulated Earnings
Balance at January 1, 2012 at Dec. 31, 2011	$ 900,987	$ 532	$ (469)	$ 497,919	$ 31,353	$ 371,652
Balance at January 1, 2012 (in shares) at Dec. 31, 2011		53,183
Increase (Decrease) in Stockholders' Equity
Net income	67,800					67,800
Other comprehensive income	27,703				27,703
Stock-based compensation	5,235			5,235
Stock-based compensation (in shares)		91
Issuance of restricted shares, net of shares remitted	(1,604)			(1,604)
Issuance of restricted shares, net of shares remitted (in shares)		(24)
Exercise of stock options	231	2		229
Exercise of stock options (in shares)		39
Net tax benefit on exercise of stock options	1,776			1,776
Net tax benefit on exercise of stock options (in shares)		97
Employee stock purchase plan	4,627			4,627
Employee stock purchase plan (in shares)		0
Balance at September 30, 2012 at Sep. 30, 2012	$ 1,006,755	$ 534	$ (469)	$ 508,182	$ 59,056	$ 439,452
Balance at September 30, 2012 (in shares) at Sep. 30, 2012		53,386