Unaudited Condensed Consolidated Statements of Stockholders' Deficit - USD ($) shares in Thousands, $ in Thousands	Total	5.75% Convertible Notes	1.50% Convertible Notes	Common Stock	Common Stock 5.75% Convertible Notes	Additional Paid-in Capital	Additional Paid-in Capital 5.75% Convertible Notes	Additional Paid-in Capital 1.50% Convertible Notes	Accumulated Losses	AOCI Attributable to Parent	Treasury Stock	Noncontrolling Interest
Beginning Balance at Dec. 31, 2016										$ (70,428)
Ending Balance at Jun. 30, 2017										(56,552)
Beginning Balance at Dec. 31, 2017	$ (50,976)			$ 90		$ 1,044,518			$ (223,718)	(51,280)	$ (844,030)	$ 23,444
Beginning Balance (in shares) at Dec. 31, 2017				90,159
Shares issued on vesting of restricted stock (in shares)				297
Shares issued on conversion of 5.75% Convertible Notes	12,694	$ 12,694			$ 11		$ 12,683
Shares issued on conversion of 5.75% Convertible Notes (in shares)					11,035
Writeoff of equity component of 1.50% Convertible Notes			$ (23,250)					$ (23,250)
Elimination of non-controlling interest related to the acquisition of additional interest in Hydraulic joint venture						2,097						(2,097)
Shares repurchased on vesting of restricted stock and exercise of stock options	(146)										(146)
Compensation expense in connection with restricted stock and stock options	1,518					1,518
Payments from non-controlling interest holders, net of imputed interest	195											195
Change in redemption value of redeemable non-controlling interest	995								995
Net (loss) income	(44,522)								(51,670)			7,148
Tax benefit related to amortization of convertible notes' discount	35					35
Foreign currency translation	(2,802)					(22)				(2,780)
Distributions to joint ventures	(5,760)											(5,760)
Ending Balance at Jun. 30, 2018	(94,303)			$ 101		$ 1,037,579			(261,030)	(50,883)	$ (844,176)	24,106
Ending Balance (in shares) at Jun. 30, 2018				101,491
Cumulative effect of accounting change for adoption | ASC 606	$ 17,716								16,540			$ 1,176
Cumulative effect of accounting change for adoption | ASU 2016-01									$ (3,177)	$ 3,177