Borrowings - Additional Information (Detail) - USD ($)		60 Months Ended
	Mar. 30, 2015	Mar. 30, 2025	Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Maximum borrowing capacity			$ 792,200,000
Outstanding borrowings with FHLB			0	$ 0
Outstanding short term letters of credit			170,200,000	55,000,000
Amount of maintained line of credit with correspondent bank - parent company			10,000,000
Amount of line of credit with correspondent bank - parent company			0
Amount of maintained federal fund lines of credit with correspondent banks			122,000,000	82,000,000
Amount of federal fund lines of credit with correspondent banks			0	0
Amount of federal fund line of credit with Federal Reserve Bank of Philadelphia			$ 0	$ 0
Fixed-to-Floating Rate, Subordinated Debt, Due in 2025 [Member] | Subordinated Debt [Member]
Debt Instrument [Line Items]
Aggregate principal amount of debt	$ 50,000,000
Net proceeds of debt	$ 49,000,000
Annual fixed rate of interest	5.10%
Redemption price percentage of principal amount of redeemed debt	100.00%
Scenario, Forecast [Member] | Fixed-to-Floating Rate, Subordinated Debt, Due in 2025 [Member] | Subordinated Debt [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Basis spread of interest rate (LIBOR)		3.544%