Credit Agreements (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2011
Amended Secured Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 450,000
Line Of Credit Facility, Term	4 years
Line Of Credit Facility Incremental Borrowing Capacity	150,000
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	150,000
Unsecured Credit Facility [Member]
Line of Credit Facility [Line Items]
Line Of Credit Facility, Capacity Terminated	$ 400,000