Commitments and Contingencies - Long-Term Natural Gas Purchase Contracts (Details) - Long-Term Natural Gas Purchase Contracts - USD ($) $ in Millions	1 Months Ended
Jun. 30, 2017	Dec. 31, 2019
Other Commitments [Line Items]
Term of agreement	5 years
Nonrefundable amount	$ 13.4
Due in 2020		$ 5.1
Due in 2021		12.5
Due in 2022		$ 11.1

Amount of contractual obligation due in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

No definition available.

Name:	us-gaap_ContractualObligationDueInNextTwelveMonths
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant