Annual report pursuant to Section 13 and 15(d)

Retirement Plans and Related Post Retirement Benefits - Assumptions Used to Calculate the Post Retirement Benefit Obligation (Detail)

v3.3.1.900
Retirement Plans and Related Post Retirement Benefits - Assumptions Used to Calculate the Post Retirement Benefit Obligation (Detail)
Dec. 31, 2015
Dec. 31, 2014
SERP    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Discount rate 4.45% 4.05%
Future average compensation increases   5.00%
SERP Medical    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Discount rate 4.45% 4.05%
Minimum | SERP    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Future average compensation increases 3.00%  
Maximum | SERP    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Future average compensation increases 5.00%