Employee Benefit Plans - Summary of Weighted-Average Asset Allocations by Asset Category (Detail)	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Assets Target Allocations [Line Items]
Total	100.00%	100.00%
Equity Securities [Member]
Defined Benefit Plan Assets Target Allocations [Line Items]
Total	69.00%	65.00%
Equity Securities [Member] | Minimum [Member]
Defined Benefit Plan Assets Target Allocations [Line Items]
Target Allocation	55.00%
Equity Securities [Member] | Maximum [Member]
Defined Benefit Plan Assets Target Allocations [Line Items]
Target Allocation	75.00%
Debt Securities [Member]
Defined Benefit Plan Assets Target Allocations [Line Items]
Total	28.00%	31.00%
Debt Securities [Member] | Minimum [Member]
Defined Benefit Plan Assets Target Allocations [Line Items]
Target Allocation	25.00%
Debt Securities [Member] | Maximum [Member]
Defined Benefit Plan Assets Target Allocations [Line Items]
Target Allocation	55.00%
Cash and Cash Equivalents [Member]
Defined Benefit Plan Assets Target Allocations [Line Items]
Total	3.00%	4.00%
Cash and Cash Equivalents [Member] | Minimum [Member]
Defined Benefit Plan Assets Target Allocations [Line Items]
Target Allocation	0.00%
Cash and Cash Equivalents [Member] | Maximum [Member]
Defined Benefit Plan Assets Target Allocations [Line Items]
Target Allocation	5.00%