Securities - Additional Information (Detail) (USD $)	6 Months Ended		12 Months Ended
	Jun. 30, 2013 Holdings	Jun. 30, 2012	Dec. 31, 2012 Holdings
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Maximum percentage of equity of one issuer	10.00%
Number of holdings greater than specified percentage of equity	0		0
Securities with aggregate par values	$ 680,200,000		$ 710,500,000
Proceed from sales - securities available-for-sale	9,265,000	42,810,000
Net unrealized security gains on the available-for-sale portfolio	1,400,000		13,000,000
Gross realized security gains	300,000	1,100,000
Gross security losses	200,000
Additional Gross realized security gains	600,000	300,000
Impaired loss relating to securities	0
Pittsburgh and Cincinnati [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Federal home loan bank stock, Total	$ 13,200,000		$ 21,300,000