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Retirement Plans - Schedule of Actuarial Assumptions Used in Determination of Net Periodic Pension Cost (Detail)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Compensation and Retirement Disclosure [Abstract]      
Weighted average discount rate 3.85% 4.67% 3.78%
Rates of increase in compensation levels 4.00% 4.00% 4.00%
Expected long-term rate of return on assets 7.25% 7.25% 7.25%