Subsequent Events (Details) (Amendment to Line of Credit [Member], USD $) In Thousands, unless otherwise specified	0 Months Ended
	Oct. 24, 2012	Oct. 25, 2012
Amendment to Line of Credit [Member]
Subsequent Event [Line Items]
Subsequent events date		Oct. 25, 2012
Description of Subsequent Event		amended and restated revolving credit agreement
Line of credit facility, increase in available borrowing capacity		$ 200,000
Line of credit facility, available borrowing capacity		$ 700,000
Line of credit facility, maturity date		2017-10-25
Commitment fee based on unused portion of line of credit facility (in hundredths)	0.225%	0.15%
Line of credit facility, variable rate basis	Eurocurrency Rate	Base Rate or Eurocurrency Rate
Line of credit facility, basis spread on variable rate	1.50%	1.25%