Summary of Fair Value of Derivative Instruments Not Designated as Hedging Instruments in Consolidated Balance Sheets (Detail) MW in Millions	Dec. 31, 2019 MW
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	3.6
Fiscal Year 2022 [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	0.1
Fiscal Year 2020 [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	2.7

Nominal number of units used to calculate payment on derivative.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

Name:	us-gaap_DerivativeNonmonetaryNotionalAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant