Subsequent Events (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended	3 Months Ended	9 Months Ended
	Jun. 30, 2013	Mar. 31, 2013	Sep. 30, 2013	Dec. 31, 2013 Subsequent Event [Member]	Sep. 30, 2013 Subsequent Event [Member]	Oct. 25, 2013 Subsequent Event [Member]	Jul. 24, 2013 Subsequent Event [Member]	Oct. 15, 2013 Senior Secured Revolving Credit Facility [Member]	Sep. 30, 2013 Senior Secured Revolving Credit Facility [Member]	Oct. 15, 2013 Senior Secured Revolving Credit Facility [Member] Subsequent Event [Member]
Subsequent Event [Line Items]
Credit Agreement, maximum borrowing capacity								$ 950	$ 1,500	$ 950
Date distribution was declared					Oct. 25, 2013
Cash distribution per unit						$ 0.4875	$ 0.4875
Date distribution will be paid					Nov. 14, 2013
Date unitholders of record					Nov. 07, 2013
Management incentive fee recognized	$ 1.3	$ 0.7	$ 2.0	$ 1.4