Changes in Equity (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	$ 1,795,179	$ 1,685,471	$ 1,787,889	$ 1,704,780
Cumulative effect of accounting change		(5,580)		(5,580)
Net income (loss)	(315,439)	27,896	(310,717)	16,954
Other comprehensive income (loss)	1,827	(1,209)	3,178	(2,087)
Share-based compensation	5,312	6,872	10,095	12,271
Issuance of common stock, net	99	(64)	(2,265)	(2,372)
Contributions from noncontrolling interests	2,581	1,000	5,379	1,000
Distributions to noncontrolling interests		(7,500)	(4,000)	(12,500)
Balance at the end of the period	1,489,559	1,712,466	1,489,559	1,712,466
Common Stock [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	50,180	49,913	50,026	49,781
Issuance of common stock, net	99	98	253	230
Balance at the end of the period	50,279	50,011	50,279	50,011
Additional Paid-in Capital [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	1,105,184	1,087,164	1,102,919	1,084,205
Share-based compensation	5,312	6,872	10,095	12,271
Issuance of common stock, net		(162)	(2,518)	(2,602)
Balance at the end of the period	1,110,496	1,093,874	1,110,496	1,093,874
Retained Earnings [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	701,325	606,121	701,681	622,007
Cumulative effect of accounting change		(3,762)		(3,762)
Net income (loss)	(320,530)	24,883	(320,886)	12,759
Balance at the end of the period	380,795	631,004	380,795	631,004
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	(44,200)	(43,596)	(45,449)	(42,718)
Other comprehensive income (loss)	1,670	(1,209)	2,919	(2,087)
Balance at the end of the period	(42,530)	(44,805)	(42,530)	(44,805)
Noncontrolling Interests [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	(17,310)	(14,131)	(21,288)	(8,495)
Cumulative effect of accounting change		(1,818)		(1,818)
Net income (loss)	5,091	3,013	10,169	4,195
Other comprehensive income (loss)	157		259
Contributions from noncontrolling interests	2,581	1,000	5,379	1,000
Distributions to noncontrolling interests		(7,500)	(4,000)	(12,500)
Balance at the end of the period	$ (9,481)	$ (17,618)	$ (9,481)	$ (17,618)