Earnings per Share and Unit (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income per common unit - diluted
Weighted Average Limited Partnership Units Outstanding, Basic			349,902	238,987
Parent Company [Member]
Earnings Per Share [Abstract]
Net income attributable to common stockholders	$ 47,841	$ 48,368	$ 100,500	$ 15,144
Weighted average common units outstanding for basic EPU (in shares)	169,424,000	170,088,000	170,056,000	148,610,000
Weighted average common units outstanding for diluted EPU (in shares)	169,682,000	170,420,000	170,291,000	148,930,000
Income per common share/unit - basic:
Continuing operations (in dollars per share)	$ 0.28	$ 0.28	$ 0.59	$ 0.10
Income per common share/unit - diluted:
Continuing operations (in dollars per share)	$ 0.28	$ 0.28	$ 0.59	$ 0.10
Partnership Interest [Member]
Earnings Per Share [Abstract]
Weighted average common units outstanding for basic EPU (in shares)	169,774,000	170,410,000	170,406,000	148,849,000
Weighted average common units outstanding for diluted EPU (in shares)	170,032,000	170,742,000	170,641,000	149,169,000
Income per common unit - basic
Continuing operations (in dollars per share)	$ 0.28	$ 0.28	$ 0.59	$ 0.10
Income per common unit - diluted
Continuing operations (in dollars per share)	$ 0.28	$ 0.28	$ 0.59	$ 0.10
Continuing Operations [Member] | Parent Company [Member]
Earnings Per Share [Abstract]
Net income attributable to common stockholders	$ 47,841	$ 48,368	$ 100,500	$ 15,144
Net income for common stock unit/holders - diluted	47,841	48,368	100,500	15,144
Continuing Operations [Member] | Partnership Interest [Member]
Earnings Per Share [Abstract]
Net income attributable to common stockholders	47,941	48,472	100,712	15,229
Net income for common stock unit/holders - diluted	$ 47,941	$ 48,472	$ 100,712	$ 15,229