Commitments & Contingencies - Long Term Contracts (Details) - Maximum	2 Months Ended
	Dec. 31, 2016
Pipeline And Storage Capacity Contracts
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Time Period	19 years
Gas Supply Reservation Fees
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Time Period	3 years
Gas Supply Purchase Commitments
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Time Period	15 years
Telecommunications And Technology Outsourcing Contracts
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Time Period	5 years