Subsequent Events (Details) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended								1 Months Ended
	Feb. 28, 2013	Jan. 31, 2013	Dec. 31, 2012	Feb. 15, 2013	Feb. 08, 2013	Jan. 15, 2013 Senior Secured Revolving Credit Facility [Member]	Jul. 31, 2012 Senior Secured Revolving Credit Facility [Member]	Apr. 30, 2012 Senior Secured Revolving Credit Facility [Member]	Feb. 28, 2013 Class B Units [Member]
Subsequent Event [Line Items]
Credit Agreement, current borrowing capacity						$ 900	$ 655	$ 730
Credit Agreement, prior current borrowing capacity						730	730	630
Cash distribution per unit					$ 0.4875
Partners capital distribution aggregate amount				32.3
Percentage of management fee converted to Class B units		80.00%
Issue of units in lieu of management fee									6,133,558
Management fee paid	$ 0.7		$ 0.7