Employee Benefit Plans - Additional Information (Detail) (Pension and Other Postretirement Benefit Plans [Member], USD $)
In Millions, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Pension and Other Postretirement Benefit Plans [Member]
 
Defined Benefit Plan Disclosure [Line Items]  
Current contribution amount $ 6.8
Additional contribution amount for remaining fiscal period $ 10.3