Segment Reporting (Details) (USD $)	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Reconciliation of NOI to net income
Net income	$ 208,053,000		$ 141,599,000
Indirect operating expenses, net of corporate income	15,271,000		10,818,000
Investments and investment management expense	1,034,000		979,000
Expensed acquisition, development and other pursuit costs	1,187,000		715,000
Interest expense, net	45,573,000	[1]	42,533,000	[1]
General and administrative expense	10,598,000		9,236,000
Equity in (income) loss of unconsolidated real estate entities	(34,566,000)		(5,223,000)
Depreciation expense	116,853,000	[1]	106,367,000	[1]
Impairment of Long-Lived Assets Held-for-use	5,788,000		0
Gain on sale of real estate assets	(70,958,000)		0
Gain on sale of discontinued operations	0		(37,869,000)
Income from discontinued operations	0		(310,000)
Net operating income from real estate assets sold or held for sale, not classified as discontinued operations	(836,000)		(4,971,000)
Net operating income	297,997,000		263,874,000
Continuing Operations
Reconciliation of NOI to net income
Net operating income	$ 297,997,000		$ 263,874,000

[1] Includes amounts associated with assets sold or held for sale, not classified as discontinued operations.