Retirement Plans - Schedule of Weighted-Average Assumptions Used to Determine Benefit Obligation (Detail) - Benefit Obligation [Member] |
12 Months Ended | ||
---|---|---|---|
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
|
Net Periodic Benefit Cost Assumptions [Line Items] | |||
Discount rate | 3.88% | 3.61% | 4.01% |
Health care cost trend: Initial | 6.25% | 6.50% | 6.75% |
Health care cost trend: Ultimate | 4.75% | 4.75% | 4.75% |
Year ultimate reached | 2022 | 2022 | 2022 |