Investment Securities - Additional Information (Detail) (USD $)	6 Months Ended
	Jun. 30, 2013 Securities	Jun. 30, 2012	Dec. 31, 2012 Securities
Investments Debt And Equity Securities [Abstract]
Transactions involving available-for-sale debt securities	$ 0	$ 0
Securities had unrealized losses for less than twelve months	24		4
Available-for-sale securities continuous unrealized loss position twelve months or longer number of securities	1		1