Derivative Instruments - Additional Information (Detail) MW in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) MW	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MW	3.6
Energy Hedges [Member]
Derivative [Line Items]
Proceeds from Hedge, Investing Activities	$ 18,000,000	$ 8,000,000	$ 17,000,000
Payments for (Proceeds from) Hedge, Investing Activities	2,000,000	24,000,000	$ 0
Interest rate swap
Derivative [Line Items]
Derivative, Notional Amount	$ 150,000,000
Fiscal Year 2022 [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MW	0.1
Fiscal Year 2020 [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MW	2.7
Fiscal Year 2021 [Member] [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MW	0.8
Fair Value, Inputs, Level 2 [Member] | Interest rate swap
Derivative [Line Items]
Derivative Liability	$ 2,000,000	0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Energy Hedges [Member]
Derivative [Line Items]
Derivative Liability	$ 0	$ 13,000,000