Shareholders' Equity/Partners' Capital - AOCI by Component (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance, value	$ 5,107,883	$ 5,007,701
Cumulative effect of accounting change				$ 14,519
Ending balance, value	5,090,892	5,024,878
Accumulated Other Comprehensive (Loss) Income
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance, value	7,664	128,682
Cumulative effect of accounting change			$ (108,374)	$ (108,374)
Net current period other comprehensive (loss) income	(16,738)	9,950
Amounts reclassified from AOCI	(2,311)
Ending balance, value	(11,385)	30,258
Marketable securities
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance, value	0	109,554
Cumulative effect of accounting change			(109,554)
Net current period other comprehensive (loss) income	0	0
Amounts reclassified from AOCI	0
Ending balance, value	0	0
Pro-rata share of nonconsolidated subsidiaries' OCI
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance, value	3,253	3,769
Cumulative effect of accounting change			(1,671)
Net current period other comprehensive (loss) income	(985)	346
Amounts reclassified from AOCI	(2,311)
Ending balance, value	(43)	2,444
Other
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance, value	(7,348)	(8,183)
Cumulative effect of accounting change			0
Net current period other comprehensive (loss) income	1,276	(654)
Amounts reclassified from AOCI	0
Ending balance, value	(6,072)	(8,837)
Interest rate swaps
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance, value	11,759	23,542
Cumulative effect of accounting change			$ 2,851
Net current period other comprehensive (loss) income	(17,029)	10,258
Amounts reclassified from AOCI	0
Ending balance, value	$ (5,270)	$ 36,651