Earnings per Share and Unit (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income per common unit - diluted
Weighted Average Limited Partnership Units Outstanding, Basic		349,902		276,503
Parent Company [Member]
Earnings Per Share [Abstract]
Net income attributable to common stockholders	$ 69,722	$ 59,666	$ 170,222	$ 74,810
Weighted average common units outstanding for basic EPU (in shares)	169,438,000	170,105,000	169,847,000	155,881,000
Weighted average common units outstanding for diluted EPU (in shares)	169,839,000	170,466,000	170,166,000	156,190,000
Income per common share/unit - basic:
Continuing operations (in dollars per share)	$ 0.41	$ 0.35	$ 1.00	$ 0.48
Income per common share/unit - diluted:
Continuing operations (in dollars per share)	$ 0.41	$ 0.35	$ 1.00	$ 0.48
Partnership Interest [Member]
Earnings Per Share [Abstract]
Weighted average common units outstanding for basic EPU (in shares)	169,788,000	170,455,000	170,197,000	156,158,000
Weighted average common units outstanding for diluted EPU (in shares)	170,189,000	170,816,000	170,516,000	156,467,000
Income per common unit - basic
Continuing operations (in dollars per share)	$ 0.41	$ 0.35	$ 1.00	$ 0.48
Income per common unit - diluted
Continuing operations (in dollars per share)	$ 0.41	$ 0.35	$ 1.00	$ 0.48
Continuing Operations [Member] | Parent Company [Member]
Earnings Per Share [Abstract]
Net income attributable to common stockholders	$ 69,722	$ 59,666	$ 170,222	$ 74,810
Net income for common stock unit/holders - diluted	69,722	59,666	170,222	74,810
Continuing Operations [Member] | Partnership Interest [Member]
Earnings Per Share [Abstract]
Net income attributable to common stockholders	69,869	59,798	170,580	75,027
Net income for common stock unit/holders - diluted	$ 69,869	$ 59,798	$ 170,580	$ 75,027