Annual report pursuant to Section 13 and 15(d)

Retirement Plans and Related Post Retirement Benefits - Assumptions Used to Determine the Net Periodic Cost (Detail)

v3.3.1.900
Retirement Plans and Related Post Retirement Benefits - Assumptions Used to Determine the Net Periodic Cost (Detail)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
SERP      
Defined Benefit Plan Disclosure      
Discount rate 4.05% 5.10% 4.20%
Future average compensation increases 5.00% 5.00% 5.00%
SERP Medical      
Defined Benefit Plan Disclosure      
Discount rate 4.05% 5.10% 4.20%
Future average compensation increases 5.32% 5.48% 5.76%