Employee Benefit Plans - Assets Allocation (Detail) - Pension Plans [Member] - Qualified Plan [Member]	Dec. 31, 2019
Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Policy target percentage	1.00%
Cash Equivalents [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Policy target percentage	0.00%
Cash Equivalents [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Policy target percentage	2000.00%
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Policy target percentage	65.00%
Equity Securities [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Policy target percentage	5500.00%
Equity Securities [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Policy target percentage	7500.00%
Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Policy target percentage	24.00%
Fixed Income Securities [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Policy target percentage	1000.00%
Fixed Income Securities [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Policy target percentage	4000.00%