Employee Benefit Plans - Weighted-Average Assumptions Used to Determine Net Periodic Benefit Cost (Detail) |
12 Months Ended | ||
|---|---|---|---|
Dec. 27, 2014 |
Dec. 28, 2013 |
Dec. 29, 2012 |
|
| Pension Benefits [Member] | |||
| Defined Benefit Plan Disclosure [Line Items] | |||
| Expected long-term rate of return on plan assets | 7.30% | 7.50% | 7.50% |
| Pension Benefits [Member] | Minimum [Member] | |||
| Defined Benefit Plan Disclosure [Line Items] | |||
| Discount rate | 4.21% | 3.30% | 3.89% |
| Pension Benefits [Member] | Maximum [Member] | |||
| Defined Benefit Plan Disclosure [Line Items] | |||
| Discount rate | 4.46% | 3.57% | 4.07% |
| Healthcare & Life Ins [Member] | |||
| Defined Benefit Plan Disclosure [Line Items] | |||
| Discount rate | 4.33% | 3.41% | 4.00% |