Schedule of Market Values of Pension Plan Assets (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 106,469	$ 104,074	$ 87,940
Equity Securities | U.S. Large Cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8,600	22,800
Equity Securities | U.S. Mid Cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,740	1,566
Equity Securities | U.S. Small-Mid Cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		7,738
Equity Securities | U.S. Small Cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,725	1,583
Equity Securities | International Developed
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,508	10,779
Equity Securities | Emerging Markets
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,154	3,912
Fixed Income Securities | Core Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	23,222
Fixed Income Securities | Long Duration Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	55,933	51,355
Fixed income securities | REIT Fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,124	3,904
Cash | Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	463	437
Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	106,469	104,074
Fair Value, Inputs, Level 2 | Equity Securities | U.S. Large Cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8,600	22,800
Fair Value, Inputs, Level 2 | Equity Securities | U.S. Mid Cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,740	1,566
Fair Value, Inputs, Level 2 | Equity Securities | U.S. Small-Mid Cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		7,738
Fair Value, Inputs, Level 2 | Equity Securities | U.S. Small Cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,725	1,583
Fair Value, Inputs, Level 2 | Equity Securities | International Developed
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,508	10,779
Fair Value, Inputs, Level 2 | Equity Securities | Emerging Markets
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,154	3,912
Fair Value, Inputs, Level 2 | Fixed Income Securities | Core Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	23,222
Fair Value, Inputs, Level 2 | Fixed Income Securities | Long Duration Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	55,933	51,355
Fair Value, Inputs, Level 2 | Fixed income securities | REIT Fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,124	3,904
Fair Value, Inputs, Level 2 | Cash | Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 463	$ 437