Notes Payable (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Notes Payable [Line Items]
Notes payable	$ 548,906	$ 478,790
Senior Notes [Member]
Notes Payable [Line Items]
Notes payable	298,906	298,790
Revolving Credit Facility [Member]
Notes Payable [Line Items]
Notes payable	$ 250,000	$ 180,000