Earnings (Losses) Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jan. 31, 2017
Net income (loss) (numerator):
Income (loss) from continuing operations, net of tax	$ (114,725)	$ (119,285)	$ (115,476)	$ (147,628)	$ (330,196)	$ (97,839)	$ (186,565)	$ (396,644)	$ (497,114)	$ (1,011,244)	$ (329,497)
Less: net (income) loss attributable to noncontrolling interest	(1,177)	(2,113)	(1,971)	(917)	(1,125)	(1,185)	2,899	(724)	(6,178)	(135)	(381)
Less: (earnings) losses allocated to unvested shareholders									13,210	22,730	7,820
Adjusted income (loss) from continuing operations, net of tax - basic									(490,082)	(988,649)	(322,058)
Income (loss) from discontinued operations, net of tax	$ (442)	$ (27,134)	$ (15,504)	$ (439)	$ (4,266)	$ (12,187)	$ (984)	$ (926)	$ (43,519)	$ (18,363)	$ (42,797)
Weighted-average number of shares outstanding - basic									280,653	276,475	282,982
Earnings (losses) Per Share - Basic
Basic from continuing operations (in dollars per share)	$ (0.40)	$ (0.42)	$ (0.41)	$ (0.52)	$ (1.17)	$ (0.35)	$ (0.65)	$ (1.41)	$ (1.75)	$ (3.58)	$ (1.14)
Basic from discontinued operations (in dollars per share)		(0.10)	(0.05)		(0.01)	(0.04)			(0.15)	(0.06)	(0.15)
Total Basic (in dollars per share)	$ (0.40)	$ (0.52)	$ (0.46)	$ (0.52)	$ (1.18)	$ (0.39)	$ (0.65)	$ (1.41)	$ (1.90)	$ (3.64)	$ (1.29)
DILUTED EPS:
Adjusted income (loss) from continuing operations, net of tax - basic									$ (490,082)	$ (988,649)	$ (322,058)
Adjusted income (loss) from continuing operations, net of tax - diluted									(490,082)	(988,649)	(322,058)
Income (loss) from discontinued operations, net of tax	$ (442)	$ (27,134)	$ (15,504)	$ (439)	$ (4,266)	$ (12,187)	$ (984)	$ (926)	$ (43,519)	$ (18,363)	$ (42,797)
Weighted-average number of shares outstanding - basic									280,653	276,475	282,982
Weighted-average number of shares outstanding - diluted									280,653	276,475	282,982
Earnings (losses) per share:
Diluted from continuing operations (in dollars per share)	$ (0.40)	$ (0.42)	$ (0.41)	$ (0.52)	$ (1.17)	$ (0.35)	$ (0.65)	$ (1.41)	$ (1.75)	$ (3.58)	$ (1.14)
Diluted from discontinued operations (in dollars per share)		(0.10)	(0.05)		(0.01)	(0.04)			(0.15)	(0.06)	(0.15)
Total Diluted (in dollars per share)	$ (0.40)	$ (0.52)	$ (0.46)	$ (0.52)	$ (1.18)	$ (0.39)	$ (0.65)	$ (1.41)	$ (1.90)	$ (3.64)	$ (1.29)
0.75% senior exchangeable notes due January 2024
Earnings (losses) per share:
Aggregate amount of senior notes	$ 575,000								$ 575,000			$ 575,000
Interest rate on senior notes due (as a percent)	0.75%								0.75%			0.75%
0.75% senior exchangeable notes due January 2024 | Minimum
Earnings (losses) per share:
Share issued price (in dollars per share)	$ 25.16								$ 25.16