Basis of Presentation and Significant Accounting Policies - Investment Tax Credits (ITC) (Additional Information) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Tax Credit Carryforward [Line Items]
ITC recapture period	5 years
ITC recaptured amount	$ 0.0	$ 0	$ 8,300,000
Minimum
Tax Credit Carryforward [Line Items]
Incentives received by the Company			1.00%
Maximum
Tax Credit Carryforward [Line Items]
Incentives received by the Company			10.00%
2017
Tax Credit Carryforward [Line Items]
Benefit of ITC	$ 45,500,000