Retirement Plans and Other Postretirement Benefits - Information for Pension Plans with Accumulated Benefit Obligation in Excess of Plan Assets (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets [Abstract]
Projected benefit obligation	$ 48,928	$ 37,912
Accumulated benefit obligation	45,003	36,683
Fair value of plan assets	$ 41,437	$ 40,547