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Benefit Plans - Expected Weighted Average Long-Term Rate of Return (Detail)
12 Months Ended
Dec. 31, 2017
Jan. 01, 2017
Defined Benefit Plan Disclosure [Line Items]    
Target Allocation 2018 100.00%  
Percentage of Plan Assets at Fiscal Year-End 100.00% 100.00%
Weighted Average Expected Long-Term Rate of Return - 2017 6.00%  
U.S. Large Capitalization Equity Securities [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Target Allocation 2018 40.00%  
Percentage of Plan Assets at Fiscal Year-End 41.00% 41.00%
Weighted Average Expected Long-Term Rate of Return - 2017 3.00%  
U.S. Small/Mid-Capitalization Equity Securities [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Target Allocation 2018 5.00%  
Percentage of Plan Assets at Fiscal Year-End 5.00% 5.00%
Weighted Average Expected Long-Term Rate of Return - 2017 0.50%  
International Equity Securities [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Target Allocation 2018 15.00%  
Percentage of Plan Assets at Fiscal Year-End 15.00% 15.00%
Weighted Average Expected Long-Term Rate of Return - 2017 1.20%  
Debt Securities [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Target Allocation 2018 40.00%  
Percentage of Plan Assets at Fiscal Year-End 39.00% 39.00%
Weighted Average Expected Long-Term Rate of Return - 2017 1.30%