UNAUDITED 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 Dec. 31, 2012	$ 1,432,072	$ 604	$ (469)	$ 880,979	$ 49,632	$ 501,326
Balance (in shares) at Dec. 31, 2012		60,385
Increase (Decrease) in Stockholders' Equity
Net income	10,502					10,502
Other comprehensive loss	(23,861)				(23,861)
Stock-based compensation	1,887			1,887
Stock-based compensation (in shares)		10
Issuance of restricted shares, net of shares remitted	(41)			(41)
Issuance of restricted shares, net of shares remitted (in shares)		(3)
Issuance costs related to 2012 issuance of common stock	(250)
Exercise of stock options	397	1		396
Exercise of stock options (in shares)		61
Net tax benefit on exercise of stock-based awards	1,216			1,216
Net tax benefit on exercise of stock options (in shares)		0
Employee stock purchase plan	1,546			1,546
Employee stock purchase plan (in shares)		38
Balance at Mar. 31, 2013	$ 1,423,468	$ 605	$ (469)	$ 885,733	$ 25,771	$ 511,828
Balance (in shares) at Mar. 31, 2013		60,491