Pension Plans - Weighted-Average Target Allocations of Plan Assets (Detail) |
12 Months Ended |
|---|---|
Dec. 31, 2016 | |
| Equity Securities [Member] | |
| Defined Benefit Plan Disclosure [Line Items] | |
| Target plan asset allocation range, Minimum | 30.00% |
| Target plan asset allocation range, Maximum | 80.00% |
| Target plan asset allocations | 60.00% |
| Fixed Income [Member] | |
| Defined Benefit Plan Disclosure [Line Items] | |
| Target plan asset allocation range, Minimum | 20.00% |
| Target plan asset allocation range, Maximum | 70.00% |
| Target plan asset allocations | 40.00% |
| Cash and Equivalents [Member] | |
| Defined Benefit Plan Disclosure [Line Items] | |
| Target plan asset allocation range, Minimum | 0.00% |
| Target plan asset allocation range, Maximum | 10.00% |