Summary of Pension Plan Assets Measured at Fair Value on Recurring Basis by Fair Value Hierarchy (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	$ 434,569	$ 384,452
Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	307,914	245,840
Fixed Income Securities
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	84,294	96,362
Pooled Investment Funds
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	22,430	22,030
Insurance Contracts
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	13,512	12,254
Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	6,419	7,966
Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	350,302	297,406
Fair Value, Inputs, Level 1 | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	307,486	245,840
Fair Value, Inputs, Level 1 | Fixed Income Securities
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	36,749	43,600
Fair Value, Inputs, Level 1 | Pooled Investment Funds
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	0	0
Fair Value, Inputs, Level 1 | Insurance Contracts
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	0	0
Fair Value, Inputs, Level 1 | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	6,067	7,966
Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	69,975	74,792
Fair Value, Inputs, Level 2 | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	0	0
Fair Value, Inputs, Level 2 | Fixed Income Securities
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	47,545	52,762
Fair Value, Inputs, Level 2 | Pooled Investment Funds
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	22,430	22,030
Fair Value, Inputs, Level 2 | Insurance Contracts
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	0	0
Fair Value, Inputs, Level 2 | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	0	0
Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	14,292	12,254
Fair Value, Inputs, Level 3 | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	428	0
Fair Value, Inputs, Level 3 | Fixed Income Securities
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	0	0
Fair Value, Inputs, Level 3 | Pooled Investment Funds
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	0	0
Fair Value, Inputs, Level 3 | Insurance Contracts
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	13,512	12,254	11,562
Fair Value, Inputs, Level 3 | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	$ 352	$ 0