Pension, Profit Sharing, and Other Employee Benefit Plans (Fair values of Company's pension plan assets) (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	$ 33,200,000	$ 33,244,000	$ 30,590,000
Quoted Prices in Active Markets for Identical Assets (Level 1)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	24,577,000	25,934,000
Significant Other Observable Inputs (Level 2)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	8,623,000	7,310,000
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:	8,623,000	7,310,000
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:	8,623,000	7,310,000
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:	143,000	137,000
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:	143,000	137,000
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:	1,381,000	3,486,000
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:	1,381,000	3,486,000
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:	2,853,000	3,916,000
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:	2,853,000	3,916,000
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:	1,881,000	1,765,000
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:	1,881,000	1,765,000
Equity Securities Financials | Significant Other Observable Inputs (Level 2)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	0	0
Equity Securities Financials | Significant Unobservable Inputs (Level 3)
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	0	0
Equity Securities Telecommunication services
Schedule Of Defined Benefit Plan Funded Status Of Plan [Line Items]
Asset Category:	1,279,000	1,401,000
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:	1,279,000	1,401,000
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:	3,769,000	3,867,000
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:	3,769,000	3,867,000
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:	3,047,000	2,705,000
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:	3,047,000	2,705,000
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:	4,378,000	3,705,000
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:	4,378,000	3,705,000
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:	2,301,000	2,496,000
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:	2,301,000	2,496,000
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:	1,190,000	1,383,000
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:	1,190,000	1,383,000
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:	2,355,000	1,073,000
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:	2,355,000	1,073,000
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:	23,053,000	22,311,000
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:	23,053,000	22,311,000
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