Retirement Plans - Allocation of Defined Benefit Pension Plans Assets by Asset Class (Detail) (Pension Plan [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 75,260	$ 74,976	$ 69,611
Cash [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	19,009	698
U.S. Large Cap [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	15,328	26,815
U.S. Mid Cap [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	5,495	10,144
International Equity [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	4,929	8,545
Core Fixed Income [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	22,834	21,317
High-Yield Fixed Income [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 7,665	$ 7,457