Changes in Equity (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	$ 1,489,559	$ 1,712,544	$ 1,787,889	$ 1,704,780
Cumulative effect of accounting change		(5,502)		(5,502)
Net income (loss)	26,721	25,436	(283,996)	42,390
Other comprehensive income (loss)	137	612	3,315	(1,475)
Share-based compensation	3,491	4,993	13,586	17,264
Issuance of common stock, net		(213)	(2,265)	(2,585)
Contributions from noncontrolling interests	1,140		6,519	1,000
Distributions to noncontrolling interests	(17,500)	(10,000)	(21,500)	(22,500)
Balance at the end of the period	1,503,548	1,733,372	1,503,548	1,733,372
Common Stock [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	50,279	50,011	50,026	49,781
Issuance of common stock, net		15	253	245
Balance at the end of the period	50,279	50,026	50,279	50,026
Additional Paid-in Capital [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	1,110,496	1,093,874	1,102,919	1,084,205
Share-based compensation	3,491	4,993	13,586	17,264
Issuance of common stock, net		(228)	(2,518)	(2,830)
Balance at the end of the period	1,113,987	1,098,639	1,113,987	1,098,639
Retained Earnings [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	380,795	631,004	701,681	622,007
Cumulative effect of accounting change		(3,762)		(3,762)
Net income (loss)	19,313	21,272	(301,573)	34,031
Balance at the end of the period	400,108	652,276	400,108	652,276
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	(42,530)	(44,805)	(45,449)	(42,718)
Other comprehensive income (loss)	236	612	3,155	(1,475)
Balance at the end of the period	(42,294)	(44,193)	(42,294)	(44,193)
Noncontrolling Interests [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	(9,481)	(17,540)	(21,288)	(8,495)
Cumulative effect of accounting change		(1,740)		(1,740)
Net income (loss)	7,408	4,164	17,577	8,359
Other comprehensive income (loss)	(99)		160
Contributions from noncontrolling interests	1,140		6,519	1,000
Distributions to noncontrolling interests	(17,500)	(10,000)	(21,500)	(22,500)
Balance at the end of the period	$ (18,532)	$ (23,376)	$ (18,532)	$ (23,376)