CONDENSED CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In- Capital	Treasury Stock	Accumulated Deficit	Noncontrolling Interest
Balances at beginning of period at Dec. 31, 2017	$ 1,530,291	$ 1,913	$ 4,126,549	$ (56,440)	$ (2,541,294)	$ (437)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(622,743)				(622,676)	(67)
Compensation expense related to restricted stock grants			14,675
Issuance of common stock under Associate Stock Purchase Plan		1	769
Restricted stock, net		28	(28)
Shares withheld for employee taxes		(4)	(2,711)
Purchase of treasury stock				0
Noncontrolling interest contribution						0
Other, net			99		280
Balances at end of period at Jun. 30, 2018	920,657	$ 1,938	4,139,353	(56,440)	(3,163,690)	(504)
Balances at beginning of period (in shares) at Dec. 31, 2017		191,276,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under Associate Stock Purchase Plan (in shares)		111,000
Restricted stock, net (in shares)		2,805,000
Shares withheld for employee taxes (in shares)		(394,000)
Purchase of treasury stock (in shares)		0
Balances at end of period (in shares) at Jun. 30, 2018		193,798,000
Balances at beginning of period at Mar. 31, 2018	1,079,561	$ 1,938	4,132,747	(56,440)	(2,998,201)	(483)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(165,509)				(165,488)	(21)
Compensation expense related to restricted stock grants			6,269
Issuance of common stock under Associate Stock Purchase Plan		0	398
Restricted stock, net		0	0
Shares withheld for employee taxes		0	(97)
Purchase of treasury stock				0
Noncontrolling interest contribution						0
Other, net			36		(1)
Balances at end of period at Jun. 30, 2018	920,657	$ 1,938	4,139,353	(56,440)	(3,163,690)	(504)
Balances at beginning of period (in shares) at Mar. 31, 2018		193,798,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under Associate Stock Purchase Plan (in shares)		49,000
Restricted stock, net (in shares)		(36,000)
Shares withheld for employee taxes (in shares)		(13,000)
Purchase of treasury stock (in shares)		0
Balances at end of period (in shares) at Jun. 30, 2018		193,798,000
Balances at beginning of period at Dec. 31, 2018	1,018,413	$ 1,968	4,151,147	(64,940)	(3,069,272)	(490)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(98,661)				(98,065)	(596)
Compensation expense related to restricted stock grants			12,386
Issuance of common stock under Associate Stock Purchase Plan		2	597
Restricted stock, net		32	(32)
Shares withheld for employee taxes		(4)	(3,101)
Purchase of treasury stock				(14,157)
Noncontrolling interest contribution						6,566
Other, net			48		0
Balances at end of period at Jun. 30, 2019	$ 866,204	$ 1,998	4,161,045	(79,097)	(3,223,222)	5,480
Balances at beginning of period (in shares) at Dec. 31, 2018	192,356,051	192,356,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under Associate Stock Purchase Plan (in shares)		96,000
Restricted stock, net (in shares)		3,320,000
Shares withheld for employee taxes (in shares)		(450,000)
Purchase of treasury stock (in shares)		(2,211,000)
Balances at end of period (in shares) at Jun. 30, 2019	193,110,916	193,111,000
Balances at beginning of period at Mar. 31, 2019	$ 917,597	$ 2,000	4,154,790	(70,940)	(3,167,752)	(501)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(56,055)				(55,470)	(585)
Compensation expense related to restricted stock grants			6,030
Issuance of common stock under Associate Stock Purchase Plan		1	299
Restricted stock, net		(3)	3
Shares withheld for employee taxes		0	(108)
Purchase of treasury stock				(8,157)
Noncontrolling interest contribution						6,566
Other, net			31		0
Balances at end of period at Jun. 30, 2019	$ 866,204	$ 1,998	$ 4,161,045	$ (79,097)	$ (3,223,222)	$ 5,480
Balances at beginning of period (in shares) at Mar. 31, 2019		194,573,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under Associate Stock Purchase Plan (in shares)		46,000
Restricted stock, net (in shares)		(214,000)
Shares withheld for employee taxes (in shares)		(16,000)
Purchase of treasury stock (in shares)		(1,278,000)
Balances at end of period (in shares) at Jun. 30, 2019	193,110,916	193,111,000