Subsequent Events (Details) (USD $)
In Millions, unless otherwise specified
6 Months Ended
Jun. 30, 2012
Subsequent Event, Revolving Credit Facility (Textual) [Abstract]  
Increase in revolving credit facility, post amendment $ 325
Original revolving credit facility, pre amendment 255
Extended maturity date Jul. 31, 2015
Decreased credit facility unused capacity fee percentage 0.50%
Original credit facility unused capacity fee percentage 0.375%
Decreased credit facility commitment fee percentage, applicable minimum outstanding amount $ 275