Schedule III Real Estate and Accumulated Depreciation (Parenthetical) (Details) (USD $)	12 Months Ended
	Dec. 31, 2013
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 1,107,341,000
Secured credit facilities, amount available	500,000,000
Line of credit facility, amount outstanding	0
FNMA
Real Estate and Accumulated Depreciation [Line Items]
Line of credit facility, amount outstanding	453,500,000
Variable interest rate (percent)	0.80%
Freddie Mac
Real Estate and Accumulated Depreciation [Line Items]
Secured credit facilities, amount available	200,000,000
Line of credit facility, amount outstanding	198,200,000
Encumbrance 1 | FNMA
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	571,800,000.0
Secured credit facilities, amount available	345,800,000
Line of credit facility, amount outstanding	345,800,000
Variable interest rate (percent)	1.33%
Encumbrance 1 | FNMA | Interest Rate Swap
Real Estate and Accumulated Depreciation [Line Items]
Number of Interest rate derivatives held (contracts)	4
Notional amount of interest rate derivatives	125,000,000
Variable rate borrowings after interest rate swaps (percent)	4.62%
Encumbrance 1 | FNMA | Interest Rate Cap
Real Estate and Accumulated Depreciation [Line Items]
Number of Interest rate derivatives held (contracts)	6
Notional amount of interest rate derivatives	165,000,000
Derivative cap interest rate (percent)	4.58%
Encumbrance 3 | Bonds [Member]
Real Estate and Accumulated Depreciation [Line Items]
Amount of bond used as encumbrance	6,800,000.0
Encumbrance 3 | Bonds [Member] | Interest Rate Cap
Real Estate and Accumulated Depreciation [Line Items]
Notional amount of interest rate derivatives	6,600,000
Derivative cap interest rate (percent)	6.00%
Derivative termination date	Oct. 24, 2017
Encumbrance 4 | Freddie Mac
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	200,000,000
Secured credit facilities, amount available	198,200,000
Line of credit facility, amount outstanding	198,200,000
Variable interest rate (percent)	0.73%
Encumbrance 4 | Freddie Mac | Interest Rate Swap
Real Estate and Accumulated Depreciation [Line Items]
Number of Interest rate derivatives held (contracts)	7
Notional amount of interest rate derivatives	94,000,000
Variable rate borrowings after interest rate swaps (percent)	4.58%
Encumbrance 4 | Freddie Mac | Interest Rate Cap
Real Estate and Accumulated Depreciation [Line Items]
Notional amount of interest rate derivatives	15,000,000
Derivative cap interest rate (percent)	5.00%
Encumbrance 5 | Fixed Rate Debt | Loan [Member]
Real Estate and Accumulated Depreciation [Line Items]
Amount of bond used as encumbrance	128,000,000
Notional amount of interest rate derivatives	128,000,000
Derivative cap interest rate (percent)	5.08%
Derivative termination date	Jun. 10, 2021
Encumbrance 6 | Bonds [Member]
Real Estate and Accumulated Depreciation [Line Items]
Amount of bond used as encumbrance	8,400,000.0
Encumbrance 6 | Bonds [Member] | Interest Rate Cap
Real Estate and Accumulated Depreciation [Line Items]
Notional amount of interest rate derivatives	8,400,000
Derivative cap interest rate (percent)	4.50%
Derivative termination date	Mar. 01, 2014
Encumbrance 7 | Bonds [Member]
Real Estate and Accumulated Depreciation [Line Items]
Amount of bond used as encumbrance	6,800,000.0
Encumbrance 7 | Bonds [Member] | Interest Rate Swap
Real Estate and Accumulated Depreciation [Line Items]
Notional amount of interest rate derivatives	6,800,000.0
Variable rate borrowings after interest rate swaps (percent)	6.00%
Derivative termination date	Oct. 15, 2017
Encumbrance 8 | Bonds [Member]
Real Estate and Accumulated Depreciation [Line Items]
Amount of bond used as encumbrance	5,700,000.0
Encumbrance 8 | Bonds [Member] | Interest Rate Cap
Real Estate and Accumulated Depreciation [Line Items]
Notional amount of interest rate derivatives	5,700,000
Derivative cap interest rate (percent)	6.00%
Derivative termination date	Oct. 31, 2017
Encumbrance 9 | Bonds [Member]
Real Estate and Accumulated Depreciation [Line Items]
Amount of bond used as encumbrance	7,500,000.0
Encumbrance 9 | Bonds [Member] | Interest Rate Cap
Real Estate and Accumulated Depreciation [Line Items]
Notional amount of interest rate derivatives	7,500,000.0
Derivative cap interest rate (percent)	6.00%
Derivative termination date	Oct. 31, 2017
Encumbrance 10 | Bonds [Member]
Real Estate and Accumulated Depreciation [Line Items]
Amount of bond used as encumbrance	3,300,000.0
Encumbrance 10 | Bonds [Member] | Interest Rate Cap
Real Estate and Accumulated Depreciation [Line Items]
Notional amount of interest rate derivatives	3,300,000.0
Derivative cap interest rate (percent)	6.00%
Derivative termination date	Oct. 31, 2017
Encumbrance 11 | Bonds [Member]
Real Estate and Accumulated Depreciation [Line Items]
Amount of bond used as encumbrance	10,400,000.0
Encumbrance 11 | Bonds [Member] | Interest Rate Swap
Real Estate and Accumulated Depreciation [Line Items]
Notional amount of interest rate derivatives	10,400,000.0
Variable rate borrowings after interest rate swaps (percent)	6.00%
Derivative termination date	Oct. 15, 2017
Encumbrance 12 | Bonds [Member]
Real Estate and Accumulated Depreciation [Line Items]
Amount of bond used as encumbrance	3,400,000.0
Encumbrance 12 | Variable Rate Debt 1 [Member] | Bonds [Member]
Real Estate and Accumulated Depreciation [Line Items]
Amount of bond used as encumbrance	500,000.0
Variable interest rate (percent)	0.908%
Encumbrance 12 | Variable Rate Debt 2 [Member] | Bonds [Member]
Real Estate and Accumulated Depreciation [Line Items]
Amount of bond used as encumbrance	2,900,000.0
Variable interest rate (percent)	0.867%
Encumbrance 12 | Variable Rate Debt 2 [Member] | Bonds [Member] | Interest Rate Cap
Real Estate and Accumulated Depreciation [Line Items]
Notional amount of interest rate derivatives	2,900,000.0
Derivative cap interest rate (percent)	6.00%
Derivative termination date	May 31, 2018
Encumbrance 13 | Bonds [Member]
Real Estate and Accumulated Depreciation [Line Items]
Amount of bond used as encumbrance	5,400,000.0
Encumbrance 13 | Variable Rate Debt 1 [Member] | Bonds [Member]
Real Estate and Accumulated Depreciation [Line Items]
Amount of bond used as encumbrance	500,000.0
Variable interest rate (percent)	0.908%
Encumbrance 13 | Variable Rate Debt 2 [Member] | Bonds [Member]
Real Estate and Accumulated Depreciation [Line Items]
Amount of bond used as encumbrance	4,900,000
Variable interest rate (percent)	0.867%
Encumbrance 13 | Variable Rate Debt 2 [Member] | Bonds [Member] | Interest Rate Cap
Real Estate and Accumulated Depreciation [Line Items]
Notional amount of interest rate derivatives	4,900,000.0
Derivative cap interest rate (percent)	6.00%
Derivative termination date	May 31, 2018
Encumbrance 14 | Bonds [Member]
Real Estate and Accumulated Depreciation [Line Items]
Amount of bond used as encumbrance	6,600,000.0
Encumbrance 14 | Bonds [Member] | Interest Rate Cap
Real Estate and Accumulated Depreciation [Line Items]
Notional amount of interest rate derivatives	6,600,000.0
Derivative cap interest rate (percent)	6.00%
Derivative termination date	Nov. 15, 2016
Encumbrance 15 | Bonds [Member]
Real Estate and Accumulated Depreciation [Line Items]
Amount of bond used as encumbrance	4,100,000.0
Encumbrance 15 | Bonds [Member] | Interest Rate Cap
Real Estate and Accumulated Depreciation [Line Items]
Notional amount of interest rate derivatives	4,100,000.0
Variable interest rate (percent)	6.00%
Derivative termination date	Nov. 15, 2016
Encumbrance 16 | Bonds [Member]
Real Estate and Accumulated Depreciation [Line Items]
Amount of bond used as encumbrance	3,600,000.0
Encumbrance 16 | Bonds [Member] | Interest Rate Cap
Real Estate and Accumulated Depreciation [Line Items]
Amount of bond used as encumbrance	3,600,000.0
Variable interest rate (percent)	6.00%
Derivative termination date	Nov. 15, 2016
Encumbrance 17 | Bonds [Member]
Real Estate and Accumulated Depreciation [Line Items]
Amount of bond used as encumbrance	13,200,000.0
Encumbrance 17 | Bonds [Member] | Interest Rate Cap
Real Estate and Accumulated Depreciation [Line Items]
Notional amount of interest rate derivatives	13,200,000.0
Derivative cap interest rate (percent)	4.50%
Derivative termination date	Mar. 01, 2014
Encumbrance 18 | FNMA
Real Estate and Accumulated Depreciation [Line Items]
Secured credit facilities, amount available	17,900,000.0
Variable interest rate (percent)	0.80%
Derivative termination date	Mar. 01, 2014
Encumbrance 21
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	4,900,000.0
Encumbrance 21 | FNMA | Interest Rate Cap
Real Estate and Accumulated Depreciation [Line Items]
Notional amount of interest rate derivatives	4,900,000.0
Derivative cap interest rate (percent)	4.50%
Derivative termination date	Mar. 01, 2014
Furniture, fixtures and equipment
Real Estate and Accumulated Depreciation [Line Items]
Estimated useful lives (years)	5 years
Interest Rate Cap 1 [Member] | Encumbrance 18 | FNMA | Interest Rate Cap
Real Estate and Accumulated Depreciation [Line Items]
Notional amount of interest rate derivatives	11,700,000.0
Derivative cap interest rate (percent)	5.00%
Derivative termination date	Mar. 01, 2014
Interest Rate Cap 2 [Member] | Encumbrance 18 | FNMA | Interest Rate Cap
Real Estate and Accumulated Depreciation [Line Items]
Notional amount of interest rate derivatives	6,200,000.0
Derivative cap interest rate (percent)	4.50%
Derivative termination date	Mar. 01, 2014
Minimum | Land improvements and buildings
Real Estate and Accumulated Depreciation [Line Items]
Estimated useful lives (years)	8 years
Maximum | Land improvements and buildings
Real Estate and Accumulated Depreciation [Line Items]
Estimated useful lives (years)	40 years
Corporate Real Estate Owned
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 0
Corporate Real Estate Owned | Beginning of Period
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Life Used for Depreciation	1 year