Derivative Instruments (Details) (USD $)	9 Months Ended			3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended			3 Months Ended		9 Months Ended
	Sep. 30, 2011	Dec. 31, 2010		Sep. 30, 2011 Realized Loss [Member] Interest Rate Swap [Member] Cash Flow Hedging [Member]	Sep. 30, 2010 Realized Loss [Member] Interest Rate Swap [Member] Cash Flow Hedging [Member]	Sep. 30, 2011 Realized Loss [Member] Cash Flow Hedging [Member]	Sep. 30, 2010 Realized Loss [Member] Cash Flow Hedging [Member]	Sep. 30, 2011 Interest Expense [Member] Interest Rate Swap [Member] Cash Flow Hedging [Member]	Sep. 30, 2010 Interest Expense [Member] Cash Flow Hedging [Member]	Sep. 30, 2011 Interest Expense [Member] Cash Flow Hedging [Member]	Sep. 30, 2010 Interest Expense [Member] Cash Flow Hedging [Member]	Sep. 30, 2011 Interest Rate Swap [Member] Swap	Sep. 30, 2011 Interest Rate Swap [Member] Cash Flow Hedging [Member]	Sep. 30, 2010 Interest Rate Swap [Member] Cash Flow Hedging [Member]	Sep. 30, 2011 Interest Rate Swap [Member] Cash Flow Hedging [Member]	Sep. 30, 2010 Interest Rate Swap [Member] Cash Flow Hedging [Member]
Impact of derivative instruments on the statement of operations and OCI
Gain (loss) on interest rate swap recognized in OCI (effective portion)													$ 658,000	$ (3,211,000)	$ 2,499,000	$ (10,307,000)
Gain (loss) reclassified from AOCI into income (effective portion)								467,000	(236,000)	1,440,000	(1,834,000)
Gain (loss) recognized in income (ineffective portion and amount excluded from effectiveness testing)
Derivative Instruments (Textual) [Abstract]
Other liabilities	342,013,000	244,345,000	[1]									1,368,000
Number of interest rate swaps												4
Additional Derivative Instruments (Textual) [Abstract]
Hedging losses included in accumulated other comprehensive income	2,035,000
Notional amount of interest rate swap	$ 46,445,000
Reclassification period of cash flow hedges	12 months

[1] NOTE: The consolidated balance sheet at December 31, 2010 has been derived from the audited financial statements at that date but does not include all of the information and footnotes required by U.S. generally accepted accounting principles for complete financial statements.