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 (loss)	Accumulated Earnings
Balance at Dec. 31, 2011	$ 900,987	$ 532	$ (469)	$ 497,919	$ 31,353	$ 371,652
Balance (in shares) at Dec. 31, 2011		53,183
Increase (Decrease) in Stockholders' Equity
Net (loss) income	129,674					129,674
Other comprehensive income	18,279				18,279
Stock-based compensation	7,494			7,494
Stock-based compensation (in shares)		168
Issuance of restricted shares, net of shares remitted	(2,912)			(2,912)
Issuance of restricted shares, net of shares remitted (in shares)		(48)
Issuance of common stock, net of issuance cost	369,520	69		369,451
Issuance of common stock, net of issuance costs (in shares)		6,900
Exercise of stock options	288	3		285
Exercise of stock options (in shares)		47
Net tax benefit on stock-based awards	2,546			2,546
Employee stock purchase plan	6,196			6,196
Employee stock purchase plan (in shares)		135
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 (loss) income	95,566					95,566
Other comprehensive income	(69,188)				(69,188)
Stock-based compensation	8,946			8,946
Stock-based compensation (in shares)		74
Issuance of restricted shares, net of shares remitted	(731)			(731)
Issuance of restricted shares, net of shares remitted (in shares)		(19)
Issuance costs related to issuances of common stock	(250)			(250)
Exercise of stock options	400	3		397
Exercise of stock options (in shares)		61
Net tax benefit on stock-based awards	1,399			1,399
Employee stock purchase plan	7,425			7,425
Employee stock purchase plan (in shares)		171
Balance at Dec. 31, 2013	1,475,639	607	(469)	898,165	(19,556)	596,892
Balance (in shares) at Dec. 31, 2013		60,672
Increase (Decrease) in Stockholders' Equity
Net (loss) income	(28,328)					(28,328)
Other comprehensive income	(91,286)				(91,286)
Stock-based compensation	8,800			8,800
Stock-based compensation (in shares)		0
Issuance of restricted shares, net of shares remitted	(2,793)	1		(2,794)
Issuance of restricted shares, net of shares remitted (in shares)		113
Repurchases of common stock	(104,341)	(20)		(104,321)
Repurchased of common stock (in shares)		(1,973)
Net tax benefit on stock-based awards	816			816
Employee stock purchase plan	4,364	1		4,363
Employee stock purchase plan (in shares)		91
Balance at Dec. 31, 2014	$ 1,262,871	$ 589	$ (469)	$ 805,029	$ (110,842)	$ 568,564
Balance (in shares) at Dec. 31, 2014		58,903