Stock-based Compensation Plans - PG/RG-PSUs Activities (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Potential payout of shares granted	23.00%
Minimum | Performance-based PG-PSUs and RG-PSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Potential payout of shares granted	0.00%
Maximum | Performance-based PG-PSUs and RG-PSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Potential payout of shares granted	200.00%