Fair Value Measurements (Narrative) (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Rabbi Trust [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Alternative investments (cost basis)	$ 4,500,000
Alternative Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Alternative investments (cost basis)	16,500,000
Alternative investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unfunded commitment for investments	6,500,000
Fair Value, Measurements, Recurring [Member] | Alternative Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Alternative investments (cost basis)	475,000
Fair Value, Measurements, Recurring [Member] | Alternative investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Alternative investments (cost basis)	475,000	565,000
Fair Value, Measurements, Nonrecurring [Member] | Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Book value of other real estate owned (OREO) and repossessed assets	6,500,000
Fair Value, Measurements, Nonrecurring [Member] | Reported Value Measurement [Member] | Alternative Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Alternative investments (cost basis)	$ 16,524,000	$ 16,582,000