Fair Value Disclosures - Additional Information (Detail) (USD $)	9 Months Ended	12 Months Ended					0 Months Ended		0 Months Ended				0 Months Ended		3 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014 Fair Value Measured on Recurring Basis [Member]	Dec. 31, 2013 Fair Value Measured on Recurring Basis [Member]	Sep. 30, 2014 Level 3 [Member] Fair Value Measured on Recurring Basis [Member]	Dec. 31, 2013 Level 3 [Member] Fair Value Measured on Recurring Basis [Member]	Jul. 01, 2014 Sterner Insurance Associates Inc [Member]	Jul. 01, 2014 Sterner Insurance Associates Inc [Member]	Jun. 17, 2014 Girard Partners [Member]	Jan. 27, 2014 Girard Partners [Member]	Jun. 17, 2014 Girard Partners [Member]	Jan. 27, 2014 Girard Partners [Member]	May 01, 2013 John T. Fretz Insurance Agency [Member]	May 01, 2013 John T. Fretz Insurance Agency [Member]	Jun. 30, 2013 Javers Group [Member]	Sep. 30, 2014 Javers Group [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Potential cash payments from contingent consideration, minimum								$ 0			$ 0			$ 0
Potential cash payments from contingent consideration, maximum								5,700,000			14,500,000			620,000
Potential cash payments from contingent consideration, period of measurement (in years)							3 years		5 years	5 years					3 years
Potential cash payments from contingent consideration, end date							Jun. 30, 2017		Dec. 31, 2018	Dec. 31, 2018			Apr. 30, 2016		Jun. 30, 2015
Remaining potential cash payments from contingent consideration, period of measurement (in years)													2 years
Reduction of other noninterest expense															959,000
Fair value of contingent consideration liability								635,000				5,500,000				0
Original potential cash payments from contingent consideration, minimum								0				0			0
Original potential cash payments from contingent consideration, maximum								5,700,000				14,500,000			1,700,000
Assets measured at fair value on a recurring basis			304,962,000	336,627,000	0	0
Valuation adjustments for loans held for sale	0	0
Carrying value of impaired loans held for investment	59,079,000	58,333,000
Valuation allowance of impaired loans held for investment	1,142,000	2,963,000
Mortgage Servicing Rights Carrying Amount Before Valuation Allowance	5,400,000	5,800,000
Mortgage Servicing Rights Valuation Allowance	0	250,000
Goodwill impairment	0
Impairment of intangible assets	$ 0