CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' (DEFICIT) EQUITY - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Retained Earnings	Treasury Stock	Total
Balance at Dec. 31, 2014	$ 355	$ 307,166	$ (1,888)	$ 178,559	$ (656)	$ 483,536
Balance (in shares) at Dec. 31, 2014	35,399,000
Increase (Decrease) in Shareholders' Equity
Net loss				(327,091)		(327,091)
Issuance of common stock upon vesting of restricted stock units	$ 3	(3)
Issuance of common stock upon vesting of restricted stock units (in shares)	306,000
Issuance of common stock in connection with the exercise of stock options	$ 1					1
Issuance of common stock in connection with the exercise of stock options (in shares)	8,000
Purchase of treasury stock		40			(40)
Purchase of treasury stock (in shares)	(2,000)
Stock-based compensation expense		11,134				11,134
Tax expense associated with vesting of restricted stock units		(596)				(596)
Effect of shares withheld to cover taxes		(2,212)				(2,212)
Tax (provision) benefit on unrealized loss on DB SERP			(81)			(81)
Total other comprehensive income (loss)			555			555
Balance at Dec. 31, 2015	$ 359	315,529	(1,414)	(148,532)	(696)	165,246
Balance (in shares) at Dec. 31, 2015	35,711,000
Increase (Decrease) in Shareholders' Equity
Net loss						(17,537)
Balance at Mar. 31, 2016						$ 148,113
Balance (in shares) at Mar. 31, 2016						35,901,426
Balance at Dec. 31, 2015	$ 359	315,529	(1,414)	(148,532)	(696)	$ 165,246
Balance (in shares) at Dec. 31, 2015	35,711,000
Increase (Decrease) in Shareholders' Equity
Net loss						(17,865)
Balance at Jun. 30, 2016						$ 149,918
Balance (in shares) at Jun. 30, 2016						36,001,739
Balance at Dec. 31, 2015	$ 359	315,529	(1,414)	(148,532)	(696)	$ 165,246
Balance (in shares) at Dec. 31, 2015	35,711,000
Increase (Decrease) in Shareholders' Equity
Net loss						(25,343)
Balance at Sep. 30, 2016						$ 144,503
Balance (in shares) at Sep. 30, 2016						36,015,526
Balance at Dec. 31, 2015	$ 359	315,529	(1,414)	(148,532)	(696)	$ 165,246
Balance (in shares) at Dec. 31, 2015	35,711,000
Increase (Decrease) in Shareholders' Equity
Net loss				(106,471)		(106,471)
Issuance of common stock upon vesting of restricted stock units	$ 3	(3)
Issuance of common stock upon vesting of restricted stock units (in shares)	330,000
Stock-based compensation expense		9,763				9,763
Tax expense associated with vesting of restricted stock units		(2,810)				(2,810)
Effect of shares withheld to cover taxes		(288)				(288)
Tax (provision) benefit on unrealized loss on DB SERP			16			16
Total other comprehensive income (loss)			(42)			(42)
Balance at Dec. 31, 2016	$ 362	322,191	(1,440)	(255,003)	(696)	$ 65,414
Balance (in shares) at Dec. 31, 2016	36,041,000					36,041,073
Balance at Mar. 31, 2016						$ 148,113
Balance (in shares) at Mar. 31, 2016						35,901,426
Increase (Decrease) in Shareholders' Equity
Net loss						$ (328)
Balance at Jun. 30, 2016						$ 149,918
Balance (in shares) at Jun. 30, 2016						36,001,739
Increase (Decrease) in Shareholders' Equity
Net loss						$ (7,478)
Balance at Sep. 30, 2016						$ 144,503
Balance (in shares) at Sep. 30, 2016						36,015,526
Increase (Decrease) in Shareholders' Equity
Net loss						$ (81,128)
Balance at Dec. 31, 2016	$ 362	322,191	(1,440)	(255,003)	(696)	$ 65,414
Balance (in shares) at Dec. 31, 2016	36,041,000					36,041,073
Increase (Decrease) in Shareholders' Equity
Net loss						$ (17,734)
Balance at Mar. 31, 2017						$ 48,491
Balance (in shares) at Mar. 31, 2017						36,259,272
Balance at Dec. 31, 2016	$ 362	322,191	(1,440)	(255,003)	(696)	$ 65,414
Balance (in shares) at Dec. 31, 2016	36,041,000					36,041,073
Increase (Decrease) in Shareholders' Equity
Net loss						$ (16,097)
Balance at Jun. 30, 2017						$ 53,026
Balance (in shares) at Jun. 30, 2017						36,335,776
Balance at Dec. 31, 2016	$ 362	322,191	(1,440)	(255,003)	(696)	$ 65,414
Balance (in shares) at Dec. 31, 2016	36,041,000					36,041,073
Increase (Decrease) in Shareholders' Equity
Net loss						$ (20,258)
Balance at Sep. 30, 2017						$ 52,433
Balance (in shares) at Sep. 30, 2017						36,343,669
Balance at Dec. 31, 2016	$ 362	322,191	(1,440)	(255,003)	(696)	$ 65,414
Balance (in shares) at Dec. 31, 2016	36,041,000					36,041,073
Increase (Decrease) in Shareholders' Equity
Net loss				(104,671)		$ (104,671)
Issuance of common stock upon vesting of restricted stock units	$ 3	(3)
Issuance of common stock upon vesting of restricted stock units (in shares)	331,000
Stock-based compensation expense		12,929				12,929
Cumulative effect of a change in accounting for stock-based payments (Note B) | ASU 2016-09		98		(98)
Effect of shares withheld to cover taxes		(1,477)				(1,477)
Tax (provision) benefit on unrealized loss on DB SERP			151			151
Total other comprehensive income (loss)			(397)			(397)
Balance at Dec. 31, 2017	$ 365	333,738	(1,686)	(359,772)	(696)	$ (28,051)
Balance (in shares) at Dec. 31, 2017	36,372,000					36,372,411
Balance at Mar. 31, 2017						$ 48,491
Balance (in shares) at Mar. 31, 2017						36,259,272
Increase (Decrease) in Shareholders' Equity
Net loss						$ 1,637
Balance at Jun. 30, 2017						$ 53,026
Balance (in shares) at Jun. 30, 2017						36,335,776
Increase (Decrease) in Shareholders' Equity
Net loss						$ (4,161)
Balance at Sep. 30, 2017						$ 52,433
Balance (in shares) at Sep. 30, 2017						36,343,669
Increase (Decrease) in Shareholders' Equity
Net loss						$ (84,413)
Balance at Dec. 31, 2017	$ 365	$ 333,738	$ (1,686)	$ (359,772)	$ (696)	$ (28,051)
Balance (in shares) at Dec. 31, 2017	36,372,000					36,372,411