Employee Benefit Plans - Summary of Weighted-Average Assets Allocation (Detail) - Pension Plan [Member] |
Dec. 31, 2017 |
Dec. 31, 2016 |
---|---|---|
Weighted-Average Assets Allocation | ||
Weighted-Average Assets Allocation | 100.00% | 100.00% |
Equity Securities [Member] | ||
Weighted-Average Assets Allocation | ||
Weighted-Average Assets Allocation | 28.92% | |
Fixed Income [Member] | ||
Weighted-Average Assets Allocation | ||
Weighted-Average Assets Allocation | 65.40% | 71.08% |
Cash [Member] | ||
Weighted-Average Assets Allocation | ||
Weighted-Average Assets Allocation | 34.60% |