Subsequent Event (Details)			2 Months Ended	3 Months Ended	9 Months Ended
	Oct. 25, 2016 MMcfe	Oct. 13, 2016 USD ($)	Dec. 31, 2016 USD ($) $ / shares	Dec. 31, 2016 USD ($) a well $ / shares	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)
Subsequent Event [Line Items]
Payments to acquire businesses, gross					$ 412,348,000	$ 0
EQM
Subsequent Event [Line Items]
Face amount					$ 750,000,000
Republic Transaction | Scenario, Forecast
Subsequent Event [Line Items]
Payments to acquire businesses, gross			$ 319,800,000
Trans Energy, Inc. | Scenario, Forecast
Subsequent Event [Line Items]
Business acquisition, share price (in dollars per share) | $ / shares			$ 3.58	$ 3.58
Republic Transaction and Trans Energy, Inc. | Scenario, Forecast
Subsequent Event [Line Items]
Number of acres acquired | a				42,600
Number of wells acquired | well				42
Number of producing wells acquired | well				33
Subsequent Event | AVC and Rager
Subsequent Event [Line Items]
Percentage of voting interests acquired		100.00%
Consideration transferred		$ 275,000,000
Subsequent Event | Republic Transaction and Trans Energy, Inc.
Subsequent Event [Line Items]
Production of well (in MMcfe) | MMcfe	42
Subsequent Event | Pennsylvania Acquisition | Scenario, Forecast
Subsequent Event [Line Items]
Payments to acquire businesses, gross				$ 170,000,000
Number of acres acquired | a				17,000
Number of producing wells acquired | well				2