Fair Value Measurements (Narrative) (Detail) (USD $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013 Alternative Investments [Member]	Sep. 30, 2013 Cost-method Investments [Member] Alternative Investments [Member]	Sep. 30, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member]	Sep. 30, 2013 Fair Value, Measurements, Recurring [Member] Alternative Investments [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] Alternative Investments [Member]	Sep. 30, 2013 Fair Value, Measurements, Recurring [Member] Cost-method Investments [Member] Rabbi Trust [Member]	Sep. 30, 2013 Fair Value, Measurements, Recurring [Member] Alternative Investments [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] Alternative Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Alternative investments			$ 18,200,000		$ 19,048,000	$ 19,523,000	$ 5,100,000	$ 804,000	$ 1,533,000
Maturity period of investments		10 years
Unfunded commitment for investments		2,000,000
Interest rate swap maturity period	30 years
Book value of other real estate owned (OREO) and repossessed assets				$ 8,000,000