Condensed Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Share Capital [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]
Beginning balance at Dec. 31, 2013		$ 10,187	$ 1,008,760	$ 410,961
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issue of shares of Common Stock		3
Repurchase of shares of Common Stock		0	0
Exercise of stock options			11,137
Stock-based compensation			6,976
Net loss				(171,339)
Ending balance at Dec. 31, 2014	$ 1,276,685	10,190	1,026,873	239,622
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issue of shares of Common Stock		0
Repurchase of shares of Common Stock		(3)	(6,613)
Exercise of stock options			602
Stock-based compensation			1,654
Net loss	(185,307)			(185,307)
Ending balance at Sep. 30, 2015	$ 1,087,018	$ 10,187	$ 1,022,516	$ 54,315