Real Estate Investments Summarized Financial Information (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Balance sheets:
Real estate under development	$ 434,371us-gaap_DevelopmentInProcess	$ 50,430us-gaap_DevelopmentInProcess
Other liabilities	32,485us-gaap_OtherLiabilities	24,871us-gaap_OtherLiabilities
Statements of operations:
Gain on sale of real estate	43,600us-gaap_GainLossOnSaleOfProperty	29,200us-gaap_GainLossOnSaleOfProperty	10,900us-gaap_GainLossOnSaleOfProperty
Interest expense	(164,551)us-gaap_InterestExpense	(116,524)us-gaap_InterestExpense	(111,888)us-gaap_InterestExpense
General and administrative	(40,878)us-gaap_GeneralAndAdministrativeExpense	(26,684)us-gaap_GeneralAndAdministrativeExpense	(24,573)us-gaap_GeneralAndAdministrativeExpense
Equity income from co-investments	39,893	55,865	41,745
Total co investment [Member]
Balance sheets:
Real estate under development	3,426,574	1,953,328
Other assets	107,902	61,578
Total assets	3,534,476	2,014,906
Debt	1,677,089	690,132
Other liabilities	91,579	125,479
Equity	1,765,808	1,199,295
Total liabilities and partners' equity	3,534,476	2,014,906
Company's share of equity	1,036,411	677,133
Statements of operations:
Property revenues	188,548	100,402	130,128
Property operating expenses	(71,419)	(37,518)	(55,990)
Net operating income	117,129	62,884	74,138
Gain on sale of real estate	23,333	146,758	106,016
Interest expense	(39,990)	(24,155)	(34,959)
General and administrative	(6,321)	(5,344)	(3,697)
Equity income from co-investments	26,798	18,703	18,051
Depreciation and amortization	(74,657)	(36,831)	(47,917)
Net income	46,292	162,015	111,632
Company's share of net income	$ 39,893	$ 55,865	$ 41,745

Total amount of equity for the company's co investment.

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The current amount of expenditures for a real estate project that has not yet been completed.

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