CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Treasury common stock	Additional paid-in capital	Retained earnings	Accumulated other comprehensive income (loss)
Beginning balance at Dec. 31, 2012	$ 2,357,392	$ 1,626	$ (4,760)	$ 1,915,627	$ 360,990	$ 83,909
Beginning balance Shares at Dec. 31, 2012		162,642,000
Issuance of common stock	9,289	$ 8	0	9,281	0	0
Issuance of common stock, shares		799,000
Stock-based compensation expense	35,851	$ 0	0	35,851	0	0
Common dividends declared ($0.16 per share)	(26,129)	0	0	0	(26,129)	0
Treasury stock issuance	0	0	1,123	(1,123)	0	0
Other comprehensive income (loss)	(77,673)	0	0	0	0	(77,673)
Net (loss) income	115,722	0	0	0	115,722	0
Ending balance at Dec. 31, 2013	2,414,452	$ 1,634	(3,637)	1,959,636	450,583	6,236
Ending balance Shares at Dec. 31, 2013		163,441,000
Issuance of common stock	398,607	$ 53	0	398,554	0	0
Issuance of common stock, shares		5,270,000
Stock-based compensation expense	42,834	$ 0	0	42,834	0	0
Common dividends declared ($0.16 per share)	(26,610)	0	0	0	(26,610)	0
Treasury stock issuance	0	0	549	(549)	0	0
Other comprehensive income (loss)	(6,236)	0	0	0	0	(6,236)
Net (loss) income	634,382	0	0	0	634,382	0
Ending balance at Dec. 31, 2014	$ 3,457,429	$ 1,687	(3,088)	2,400,475	1,058,355	0
Ending balance Shares at Dec. 31, 2014	168,711,131	168,711,131
Issuance of common stock	$ 10,073	$ 6	0	10,067	0	0
Issuance of common stock, shares		665,000
Stock-based compensation expense	36,496	$ 0	0	36,496	0	0
Tax benefit related to stock-based compensation	(3,572)	0	0	(3,572)	0	0
Common dividends declared ($0.16 per share)	(27,083)	0	0	0	(27,083)	0
Treasury stock issuance	0	0	843	(843)	0	0
Net (loss) income	(713,685)	0	0	0	(713,685)	0
Ending balance at Dec. 31, 2015	$ 2,759,658	$ 1,693	$ (2,245)	$ 2,442,623	$ 317,587	$ 0
Ending balance Shares at Dec. 31, 2015	169,375,743	169,375,743