Pension and Other Postretirement Benefits - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Pension benefit plan change in discount rate	4.10%
Remeasurement of Pension Plan Liability [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Pension benefit plan curtailment charge	$ 1,217
Pension benefit plan decrease in liability	(9,300)
Pension benefit plan change in discount rate	4.00%
Pension benefit plan increase in liability due to discount change	$ 2,800