Subsequent Events (Details) $ / shares in Units, a in Thousands	Jul. 03, 2015 USD ($)	Jul. 02, 2015 a	Aug. 05, 2015 USD ($)	Aug. 04, 2015 USD ($)	Jul. 21, 2015 $ / shares	Jun. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)	Apr. 02, 2014 USD ($)
Subsequent Event [Line Items]
Long-term debt, gross						$ 985,000,000	$ 959,000,000
Credit facility due 2019
Subsequent Event [Line Items]
Maximum borrowing capacity						700,000,000		$ 1,500,000,000
Long-term debt, gross						135,000,000	$ 109,000,000
Remaining borrowing capacity						$ 564,900,000
Subsequent Event [Member]
Subsequent Event [Line Items]
Distributions declared and paid (in dollars per share) | $ / shares					$ 0.35
Subsequent Event [Member] | Credit facility due 2019
Subsequent Event [Line Items]
Maximum borrowing capacity			$ 950,000,000	$ 700,000,000
Long-term debt, gross			554,000,000
Remaining borrowing capacity			$ 396,000,000
Subsequent Event [Member] | Preferred Unit Series A
Subsequent Event [Line Items]
Distributions declared and paid (in dollars per share) | $ / shares					0.166667
Subsequent Event [Member] | Preferred Unit Series B
Subsequent Event [Line Items]
Distributions declared and paid (in dollars per share) | $ / shares					$ 0.166667
Subsequent Event [Member] | Development Agreement [Member]
Subsequent Event [Line Items]
Undeveloped oil and gas properties (in acres) | a		6
Asset Acquisition Agreement, Working Interest		87.50%
Asset Acquisition Agreement, Investor Funding		95.00%
Asset Acquisition Agreement, ROI Hurdle		1.0
Asset Acquisition Agreement, Company Funding		5.00%
Asset Acquisition Agreement, Retention of Interest Prior to ROI Hurdle		12.50%
Asset Acquisition Agreement, Investor Interest, ROI Hurdle Achievement		63.00%
Asset Acquisition Agreement, Company Interest, ROI Hurdle Achievement		37.00%
Asset Acquisition Agreement, IRR Hurdle		15.00%
Asset Acquisition Agreement, Investor Interest, IRR Hurdle Achievement		15.00%
Asset Acquisition Agreement, Company Interest, IRR Hurdle Achievement		85.00%
Subsequent Event [Member] | WGR Purchase Agreement [Member]
Subsequent Event [Line Items]
Membership interests intended to acquire	100.00%
Acquisition purchase price	$ 154,000,000
Subsequent Event [Member] | Anadarko Purchase and Sale Agreement [Member]
Subsequent Event [Line Items]
Acquisition purchase price	$ 286,000,000