Consolidated Statements of Changes in Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]	Total
Balance (in shares) at Dec. 31, 2013	54,604
Balance at Dec. 31, 2013	$ 546	$ 254,188		$ 441,417	$ 696,151
Issuance of restricted shares, net of forfeitures (in shares)	723
Issuance of restricted shares, net of forfeitures	$ 7	(7)
Employee tax withholding on restricted shares vesting (in shares)	(153)
Employee tax withholding on restricted shares vesting	$ (2)	(4,376)			$ (4,378)
Issuance of common shares for stock options exercised (in shares)	159				159
Issuance of common shares for stock options exercised	$ 2	831			$ 833
Tax effect of share-based compensation		2,118			2,118
Share-based compensation		18,350			18,350
Net income (loss)				68,823	68,823
Foreign currency translation gain (loss), net of tax			$ (45)		(45)
Balance (in shares) at Dec. 31, 2014	55,333
Balance at Dec. 31, 2014	$ 553	271,104	(45)	510,240	781,852
Issuance of restricted shares, net of forfeitures (in shares)	2,613
Issuance of restricted shares, net of forfeitures	$ 26	3,006			3,032
Employee tax withholding on restricted shares vesting (in shares)	(222)
Employee tax withholding on restricted shares vesting	$ (2)	(2,619)			$ (2,621)
Issuance of common shares for stock options exercised (in shares)	154				154
Issuance of common shares for stock options exercised	$ 2	451			$ 453
Tax effect of share-based compensation		(2,367)			(2,367)
Share-based compensation		18,549			18,549
Net income (loss)				(872,542)	(872,542)
Foreign currency translation gain (loss), net of tax			(3,980)		(3,980)
Balance (in shares) at Dec. 31, 2015	120,420
Balance at Dec. 31, 2015	$ 1,204	997,766	(4,025)	(362,302)	632,643
Stock Issued During Period, Shares, New Issues	62,542
Issuance of common shares, net of issuance costs	$ 625	709,642			710,267
Employee tax withholding on restricted shares vesting (in shares)	(314)
Employee tax withholding on restricted shares vesting	$ (3)	(494)			$ (497)
Issuance of common shares for stock options exercised (in shares)
Tax effect of share-based compensation		(5,592)			$ (5,592)
Share-based compensation		17,740			17,740
Net income (loss)				(944,289)	(944,289)
Foreign currency translation gain (loss), net of tax			1,425		1,425
Balance (in shares) at Dec. 31, 2016	119,530
Balance at Dec. 31, 2016	$ 1,195	1,009,426	$ (2,600)	$ (1,306,591)	$ (298,570)
Forfeitures of restricted shares (in shares)	(576)
Forfeitures of restricted shares	$ (6)	$ 6