Employee Benefits - Narrative (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Nov. 01, 2020	Oct. 31, 2020
Primary Beneficiary
Defined Benefit Plan, Plan Assets, Category [Line Items]
Rabbi trust investments	$ 94,005	$ 91,683
Primary Beneficiary | Equities
Defined Benefit Plan, Plan Assets, Category [Line Items]
Rabbi trust investments	80,490	$ 78,727
Pension Plan
Defined Benefit Plan, Plan Assets, Category [Line Items]
Decrease in non-service cost expense	3,800
Discretionary employer contributions to defined benefit plans	$ 32,500
Qualified Plan | Pension Plan
Defined Benefit Plan, Plan Assets, Category [Line Items]
Contribution credits rate				3.50%
Nonqualified Plan | Pension Plan
Defined Benefit Plan, Plan Assets, Category [Line Items]
Contribution credits rate			5.00%