Organization, Basis of Presentation, and Significant Accounting Policies (Details 2) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accounting Policies [Abstract]
Minimum distribution of adjusted taxable income for deducting dividends from federally taxable income (as a percent)									90.00%
Minimum distribution of REIT taxable income for federal income tax exemption (as a percent)									100.00%
Income Taxes [Line Items]
Unrecognized tax benefits	$ 0				$ 0				$ 0	$ 0
Excise and Sales Taxes									0	0	$ 0
Excise Tax Refund	0				0				0	0	0
Income tax expense									1,861	9,368	0
Casualty (gain) loss and impairment loss, net									(10,542)	0	0
Other than Temporary Impairment Losses, Investments									0	0	0
Reconciliation of Income from Book Basis to Tax Basis Adjustment
Net income attributable to common stockholders	155,428	$ 206,142	$ 172,324	$ 208,144	142,642	$ 241,100	$ 158,086	$ 141,739	742,038	683,567	353,141
GAAP gain on sale of communities (in excess of) less than tax gain									(43,873)	22,127	29,388
Depreciation/amortization timing differences on real estate									(3,105)	(10,735)	180,293
Deductible acquisition costs									0	0	(26,427)
Amortization of debt/mark to market interest									(64,676)	(38,202)	(31,965)
Tax compensation expense less than (in excess of) GAAP									(5,696)	(5,252)	12,886
Casualty (gain) loss and impairment loss, net									(10,542)	0	0
Other adjustments									(38,553)	14,323	1,018
Taxable net income									$ 575,593	$ 665,828	$ 518,334
Tax components of common stock dividends declared
Ordinary income (as a percent)									83.00%	62.00%	42.00%
15% capital gain (20% for 2013) (as a percent)									12.00%	29.00%	40.00%
Capital gain tax rate (as a percent)									20.00%	20.00%	20.00%
Unrecaptured 1250 gain (as a percent)									5.00%	9.00%	18.00%
Unsecured notes
Deferred Financing Costs
Accumulated amortization of deferred finance costs	11,995				8,833				$ 11,995	$ 8,833
Secured notes
Deferred Financing Costs
Accumulated amortization of deferred finance costs	12,315				12,255				12,315	12,255
Line of Credit [Member]
Deferred Financing Costs
Accumulated amortization of deferred finance costs	$ 4,967				$ 3,356				$ 4,967	$ 3,356