Employee Benefit Plans - Employee Pension and Other Postretirement Plans (Detail)	3 Months Ended
	Mar. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Average compensation term on which pension plan benefits are based, in years	5 years
Average compensation term within last ten years on which pension plan benefits are based, in years	5 years
Term considered when determining employee pension benefits, in years	10 years
Minimum age requirement to participate in pension plan, years	18 years
Minimum service hours per year requirement to participate in pension plan	1000 hours
People's Qualified Plan
Defined Benefit Plan Disclosure [Line Items]
Percentage of covered employee's eligible compensation	3.00%