Commitments and Contingencies (Details) - USD ($)	1 Months Ended	12 Months Ended			24 Months Ended
	May 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016
Other Commitments [Line Items]
Supplemental environmental projects	$ 178,780
Reduced penalty	$ 44,695
Rental Expense for office buildings and oil and gas operations equipment		$ 76,000,000	$ 84,000,000	$ 69,000,000
Consent Decree
Other Commitments [Line Items]
Civil penalty			$ 4,950,000		$ 54,700,000
Mitigation projects		4,500,000
Supplemental environmental projects		4,000,000
Marcellus Shale Firm Transportation Agreement
Other Commitments [Line Items]
Long-term Purchase Commitment, Amount		2,100,000,000
United States
Other Commitments [Line Items]
Long-term Purchase Commitment, Amount		$ 900,000,000
Minimum | Marcellus Shale Firm Transportation Agreement
Other Commitments [Line Items]
Commitment Obligation, Term		1 year
Minimum | United States
Other Commitments [Line Items]
Commitment Obligation, Term		1 year
Maximum | Marcellus Shale Firm Transportation Agreement
Other Commitments [Line Items]
Commitment Obligation, Term		32 years
Maximum | United States
Other Commitments [Line Items]
Commitment Obligation, Term		12 years