Fair values of Company's pension plan assets (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	$ 33,244	$ 30,590	$ 29,341
Quoted Prices in Active Markets for Identical Assets (Level 1)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	25,934	21,307
Significant Other Observable Inputs (Level 2)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	7,310	9,283
Significant Unobservable Inputs (Level 3)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	0	0
Fixed income securities U. S. Government Agencies
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	0	0
Fixed income securities U. S. Government Agencies | Quoted Prices in Active Markets for Identical Assets (Level 1)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	0	0
Fixed income securities U. S. Government Agencies | Significant Other Observable Inputs (Level 2)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	0	0
Fixed income securities U. S. Government Agencies | Significant Unobservable Inputs (Level 3)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	0	0
Fixed income securities Corporate bonds
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	7,310	9,283
Fixed income securities Corporate bonds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	0	0
Fixed income securities Corporate bonds | Significant Other Observable Inputs (Level 2)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	7,310	9,283
Fixed income securities Corporate bonds | Significant Unobservable Inputs (Level 3)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	0	0
Fixed income securities Other
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	137	153
Fixed income securities Other | Quoted Prices in Active Markets for Identical Assets (Level 1)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	137	153
Fixed income securities Other | Significant Other Observable Inputs (Level 2)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	0	0
Fixed income securities Other | Significant Unobservable Inputs (Level 3)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	0	0
Cash and certificates of deposit
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	3,486	3,253
Cash and certificates of deposit | Quoted Prices in Active Markets for Identical Assets (Level 1)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	3,486	3,253
Cash and certificates of deposit | Significant Other Observable Inputs (Level 2)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	0	0
Cash and certificates of deposit | Significant Unobservable Inputs (Level 3)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	0	0
Equity Securities Industrials
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	3,916	2,676
Equity Securities Industrials | Quoted Prices in Active Markets for Identical Assets (Level 1)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	3,916	2,676
Equity Securities Industrials | Significant Other Observable Inputs (Level 2)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	0	0
Equity Securities Industrials | Significant Unobservable Inputs (Level 3)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	0	0
Equity Securities Financials
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	1,765	2,353
Equity Securities Financials | Quoted Prices in Active Markets for Identical Assets (Level 1)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	1,765	2,353
Equity Securities Telecommunication services
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	1,401	1,121
Equity Securities Telecommunication services | Quoted Prices in Active Markets for Identical Assets (Level 1)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	1,401	1,121
Equity Securities Telecommunication services | Significant Other Observable Inputs (Level 2)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	0	0
Equity Securities Telecommunication services | Significant Unobservable Inputs (Level 3)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	0	0
Equity Securities Consumer
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	3,867	3,515
Equity Securities Consumer | Quoted Prices in Active Markets for Identical Assets (Level 1)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	3,867	3,515
Equity Securities Consumer | Significant Other Observable Inputs (Level 2)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	0	0
Equity Securities Consumer | Significant Unobservable Inputs (Level 3)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	0	0
Equity Securities Health care
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	2,705	1,900
Equity Securities Health care | Quoted Prices in Active Markets for Identical Assets (Level 1)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	2,705	1,900
Equity Securities Health care | Significant Other Observable Inputs (Level 2)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	0	0
Equity Securities Health care | Significant Unobservable Inputs (Level 3)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	0	0
Equity Securities Information technology
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	3,705	2,328
Equity Securities Information technology | Quoted Prices in Active Markets for Identical Assets (Level 1)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	3,705	2,328
Equity Securities Information technology | Significant Other Observable Inputs (Level 2)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	0	0
Equity Securities Information technology | Significant Unobservable Inputs (Level 3)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	0	0
Equity Securities Energy
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	2,496	2,645
Equity Securities Energy | Quoted Prices in Active Markets for Identical Assets (Level 1)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	2,496	2,645
Equity Securities Energy | Significant Other Observable Inputs (Level 2)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	0	0
Equity Securities Energy | Significant Unobservable Inputs (Level 3)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	0	0
Equity Securities Materials
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	1,383	1,207
Equity Securities Materials | Quoted Prices in Active Markets for Identical Assets (Level 1)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	1,383	1,207
Equity Securities Materials | Significant Other Observable Inputs (Level 2)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	0	0
Equity Securities Materials | Significant Unobservable Inputs (Level 3)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	0	0
Equity Securities Other
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	1,073	156
Equity Securities Other | Quoted Prices in Active Markets for Identical Assets (Level 1)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	1,073	156
Equity Securities Other | Significant Other Observable Inputs (Level 2)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	0	0
Equity Securities Other | Significant Unobservable Inputs (Level 3)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	0	0
Total equity securities
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	22,311	17,901
Total equity securities | Quoted Prices in Active Markets for Identical Assets (Level 1)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	22,311	17,901
Total equity securities | Significant Other Observable Inputs (Level 2)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	0	0
Total equity securities | Significant Unobservable Inputs (Level 3)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	$ 0	$ 0