Derivative Instruments and Hedging Activities (Details) (USD $)	6 Months Ended
	Jun. 30, 2011
Derivative [Line Items]
Derivatives net liability	$ 1,500,000
Not Designated as Hedging Instrument [Member] | Swap [Member]
Derivative [Line Items]
Amount of hedged item	38,000,000
Description of hedged item	Company pays a variable amount equal to the SIFMA Index plus a fixed spread on a notional amount that increases over year term of the swap increases ratably to 38.0 million. In return, Citibank pays an amount equal to the coupon on the Bonds multiplied by the outstanding par value of the bonds
Notional amount fixed spread basis	35,200,000
Term of swap (in years)	3
Notional amount fixed spread ratably increases over term of swap	38,000,000
Percentage of price depreciation the Company obligated to pay if bonds decline in value	100.00%
Percentage of price appreciation Citibank obligated to pay if bonds increase in value	85.00%
Fair value of the swap	1,600,000
Designated as Hedging Instrument [Member] | Interest Rate Cap [Member]
Derivative [Line Items]
Number of interest rate cap contracts	12
Interest rate cap contracts notional amount	191,900,000
Tax exempt variable rate debt	213,000,000
Aggregate carrying value of the interest rate cap contracts	100,000
Forward Starting Swaps [Member] | Other Comprehensive Income (Loss) [Member]
Derivative [Line Items]
Remaining forward starting swaps settled	20,000,000
Payment to counterparty for settled forward starting swaps	2,300,000
Accumulated Other Comprehensive Income (Loss) [Member]
Derivative [Line Items]
Change in fair value of derivatives	$ 4,109,000