Benefit Plans - Weighted Average Assumptions Used to Determine Benefit Obligations (Detail)	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.00%	3.70%	4.40%
Expected long term rate of return on plan assets	7.50%	7.50%	7.50%
Rate of compensation increase, minimum rate	3.50%	3.50%	3.50%
Rate of compensation increase, maximum rate	5.50%	5.50%	5.50%
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.70%	3.40%	4.20%
Expected long term rate of return on plan assets	5.30%	5.30%	5.30%