Borrowings - Additional Information (Detail) - USD ($)	Mar. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 1,300,000,000
Outstanding short term letters of credit	178,800,000	$ 148,500,000
Amount of maintained federal fund lines of credit with correspondent banks	327,000,000	302,000,000
Outstanding amount of federal fund line of credit with Federal Reserve Bank of Philadelphia	0	$ 0
Amount of maintained line of credit with correspondent bank - parent company	10,000,000
Outstanding amount of line of credit with correspondent bank - parent company	0
Federal Home Loan Bank Advances [Member]
Debt Instrument [Line Items]
Long-term debt with call option	50,800,000
Securities Sold under Agreements to Repurchase [Member]
Debt Instrument [Line Items]
Long-term debt with fixed interest rate	5,200,000
Securities Sold under Agreements to Repurchase [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Long-term debt with variable interest rate	$ 26,000,000