Consolidated Statements of Stockholders' Equity (Deficit) Statement - USD ($) $ in Thousands		Total		Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings (Accumulated Deficit) [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	February 2018 Notes [Member]	February 2018 Notes [Member] Additional Paid-in Capital [Member]
Noncontrolling Interest in Variable Interest Entity		$ 0
Beginning Balance (in shares) at Dec. 31, 2014				162,186,482
Beginning Balance at Dec. 31, 2014		$ 460,437		$ 1,622	$ (119,874)	$ 575,740	$ 2,949
Issuance of common stock under employee benefit plans (in Shares)		758,533
Issuance of common stock under employee benefit plans		$ 0		$ (8)	(8)
Stock Issued During Period, Shares, Conversion of Convertible Securities		1,341,600
Stock Issued During Period, Value, Conversion of Convertible Securities		$ 13
Adjustments to Additional Paid in Capital, Convertible Debt with Conversion Feature		100			87
Stock-based compensation expense		2,045
Adjustments to Additional Paid in Capital, Income Tax Deficiency from Share-based Compensation		(233)
Dividends declared, Retained Earnings adjustment		(98,499)				(98,499)
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest		332,102
Statement of Comprehensive Income [Abstract]
Net Income (Loss) Attributable to Parent		332,795				332,795
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Tax		71	[1]				71
Total comprehensive income		332,102
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax		(764)	[2]				(764)
Ending Balance (in shares) at Dec. 31, 2015				164,286,615
Ending Balance at Dec. 31, 2015		695,952		$ 1,643	(117,983)	810,036	2,256
Noncontrolling Interest in Variable Interest Entity		$ 0
Issuance of common stock under employee benefit plans (in Shares)		1,251,832
Issuance of common stock under employee benefit plans		$ 0		(12)	(12)
Adjustments to Additional Paid in Capital, Convertible Debt with Conversion Feature		620
Issuance of convertible debt								$ 25,465	$ 25,465
Purchase of purchased call options, net of tax		14,400
Adjustments to Additional Paid in Capital, Other		(3,977)
Stock-based compensation expense		3,741
Adjustments to Additional Paid in Capital, Income Tax Deficiency from Share-based Compensation		(462)
Dividends declared, Retained Earnings adjustment		(16,526)				(16,526)
Proceeds from Divestiture of Interest in Subsidiaries and Affiliates		250
Noncontrolling Interest, Increase from Subsidiary Equity Issuance		4,227
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest		61,403
Statement of Comprehensive Income [Abstract]
Net Income (Loss) Attributable to Parent		63,606				63,606
Net Income (Loss) Attributable to Nonredeemable Noncontrolling Interest		53
Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest		63,659
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Tax		(435)	[1]				(435)
Total comprehensive income		61,350
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax		$ (1,821)	[2]				(1,821)
Ending Balance (in shares) at Dec. 31, 2016		165,538,447
Ending Balance at Dec. 31, 2016		$ 751,143		1,655	(107,628)	857,116	0
Noncontrolling Interest in Variable Interest Entity		4,280
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		$ 755,423
Issuance of common stock under employee benefit plans (in Shares)		1,582,698
Issuance of common stock under employee benefit plans				(16)	(16)
Adjustments to Additional Paid in Capital, Convertible Debt with Conversion Feature		$ 5,967
Adjustments to Additional Paid in Capital, Other		2,063
Other Noncontrolling Interests		(4,233)
Stock-based compensation expense		$ 3,138
Stock Repurchased During Period, Shares		(13,346,389)
Treasury Stock, Retired, Par Value Method, Amount		$ (133)
Treasury Stock, Retired, Cost Method, Amount		(29,867)
Stock Repurchased and Retired During Period, Value		(30,000)
Payments to Acquire Additional Interest in Subsidiaries		(2,170)
Cumulative Effect on Retained Earnings, Net of Tax		7,617
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest		111,882
Statement of Comprehensive Income [Abstract]
Net Income (Loss) Attributable to Parent		110,748				110,748
Net Income (Loss) Attributable to Nonredeemable Noncontrolling Interest		(47)
Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest		110,701
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Tax		1,181	[1]				1,181
Total comprehensive income		111,929
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	[2]	$ 0
Ending Balance (in shares) at Dec. 31, 2017		153,774,756
Ending Balance at Dec. 31, 2017		$ 845,890		$ 1,538	$ (102,443)	$ 945,614	$ 1,181
Noncontrolling Interest in Variable Interest Entity		0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		$ 845,890

[1] Net of tax of $314, ($234) and $38 for the years ended December 31, 2017, 2016 and 2015, respectively.

[2] Net of tax of zero, ($981) and ($411) for the years ended December 31, 2017, 2016 and 2015, respectively.