Borrowed Funds - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Jun. 30, 2013
Debt Instrument [Line Items]
Junior Subordinated Debentures Amount Outstanding	$ 357,917,000	$ 358,019,000
Redeemed junior subordinated Debentures	69,200,000
(Loss)/gain on debt redemptions	$ (2,300,000)