Recourse Debt and Interest Rate Swap Narrative (Details) (USD $)	3 Months Ended			6 Months Ended	9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010	Jun. 30, 2011	Sep. 30, 2011		Sep. 30, 2010	Oct. 31, 2011	Jun. 10, 2011	Dec. 31, 2010		Apr. 09, 2010
Term Loan, Weighted-Average Interest Rates	3.646%	[1],[2]			3.646%	[1],[2]				4.396%	[2],[3]
Previous Term Loan Facility												$ 425,000,000
Borrowings Under Credit Agreement	371,875,000	[2]			371,875,000	[2]				403,750,000	[2]
Closing costs									1,800,000
Revolving credit facility	200,000,000				200,000,000
Previous Revolving Credit Facility								200,000,000
Facility fee in basis for revolving credit facility	15				15
Final payment due upon expiration				28,300,000
Liability on swap agreement	16,800,000				16,800,000					11,700,000
Amount of swap liability to be reclassified during next twelve months	6,900,000				6,900,000
Amount of swap liability reclassified during the period	2,100,000		2,200,000		6,300,000		4,300,000
Borrowings Under Credit Agreement At Date Of Amendment [Member]
Borrowings Under Credit Agreement									382,500,000
Libor Spread [Member]
Revolving Credit Facility Spread in Basis Points	110				110
Term Loan Quarterly Payment First Three Years [Member]
Required principal payments per quarter for the term loan				10,600,000
Term Loan Quarterly Payment Years Four And Five [Member]
Required principal payments per quarter for the term loan				$ 28,300,000

[1] As of September 30, 2011. See additional information below regarding the interest rate fixed at 3.646% in connection with an interest rate swap, which expires on April 1, 2015.

[2] The term loan borrowings under the Credit Agreement expire on June 10, 2016.

[3] As of December 31, 2010.