Loans and Leases - Outstanding Principal Balance and Related Carrying Amounts (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Total Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding principal balance	$ 3,543	$ 3,604
Carrying amount	3,441	3,471
VIST Financial Corp. (VIST Financial) | Acquired Credit Impaired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding principal balance	13,290	14,337
Carrying amount	11,309	11,962
VIST Financial Corp. (VIST Financial) | Acquired Non-Credit Impaired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding principal balance	262,362	301,128
Carrying amount	260,159	298,615
VIST Financial Corp. (VIST Financial) | Total Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding principal balance	275,652	315,465
Carrying amount	$ 271,468	$ 310,577