Co-investments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Equity Method Investment, Summarized Financial Information, Assets [Abstract]
Real estate under development	$ 339,386us-gaap_DevelopmentInProcess		$ 429,096us-gaap_DevelopmentInProcess
Equity Method Investment, Summarized Financial Information, Liabilities and Equity [Abstract]
Other liabilities	33,607us-gaap_OtherLiabilities		32,444us-gaap_OtherLiabilities
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
Interest expense	(47,546)us-gaap_InterestExpense	(29,041)us-gaap_InterestExpense
General and administrative	(10,545)us-gaap_GeneralAndAdministrativeExpense	(7,583)us-gaap_GeneralAndAdministrativeExpense
Equity income in co-investments	4,311	10,526
Total co investment [Member]
Equity Method Investment, Summarized Financial Information, Assets [Abstract]
Real estate under development	3,425,781		3,426,574
Other assets	181,856		107,902
Total assets	3,607,637		3,534,476
Equity Method Investment, Summarized Financial Information, Liabilities and Equity [Abstract]
Debt	1,450,210		1,568,398
Other liabilities	158,909		91,579
Equity	1,998,518		1,874,499
Total liabilities and equity	3,607,637		3,534,476
Company's share of equity	1,057,298		1,042,423
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
Property revenues	63,498	27,960
Property operating expenses	(22,954)	(11,560)
Net operating income	40,544	16,400
Gain on sale of real estate	14	11,369
Interest expense	(11,316)	(6,023)
General and administrative	(1,606)	(1,388)
Equity income in co-investments	0	4,759
Depreciation and amortization	(25,381)	(10,693)
Net income	2,255	14,424
Company's share of net income	$ 4,311	$ 10,526

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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The amount of the cost of sales reported by an equity method investment of the entity.

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Amount of equity, including noncontrolling interest, reported by an equity method investment of the entity.

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The amount of gross profit (loss) reported by an equity method investment of the entity.

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The amount of liabilities reported by an equity method investment of the entity.

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The amount of liabilities and equity reported by an equity method investment of the entity.

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The amount of net income (loss) reported by an equity method investment of the entity.

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The amount of revenue from sale of goods and services reduced by sales returns, allowances, and discounts reported by an equity method investment of the entity.

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Amount of gain (loss) on sale or disposal of oil and gas property or timber property.

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The aggregate total of expenses of managing and administering the affairs of an entity, including affiliates of the reporting entity, which are not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

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Amount of the cost of borrowed funds accounted for as interest expense.

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The other noncash expense, not otherwise specified in the taxonomy, charged against earnings in the period to allocate the cost of tangible and intangible assets over their remaining economic lives.

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