Fair Values of Assets and Liabilities - Carrying Amounts and Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Carrying Amount [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	$ 68,163	$ 66,644
Interest-bearing deposits	30,457	2,808
Securities available for sale, at fair value	855,333	886,560
Held-to-maturity Securities	405,976
Other investments	58,087
Loans Held for sale, Amount	11,613	5,763
Loans and Leases Receivable, Net of Deferred Income	4,843,776	4,683,750
Deposits	4,394,520	4,195,894
Short-term borrowings	1,464,687	1,510,825
Subordinated debt	72,167	72,167
Long-term debt	9,034	9,314
Estimate of Fair Value Measurement [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	68,163	66,644
Interest-bearing deposits	30,457	2,808
Securities available for sale, at fair value	855,333	886,560
Held-to-maturity Securities	414,770
Other investments	58,087	62,952
Loans Held for sale, Amount	11,613	5,763
Loans and Leases Receivable, Net of Deferred Income	4,857,127	4,690,852
Deposits	4,395,297	4,198,817
Short-term borrowings	1,464,408	1,510,718
Subordinated debt	61,427	62,794
Long-term debt	10,077	9,834
Estimate of Fair Value Measurement [Member] | Level 1 [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	68,163	66,644
Interest-bearing deposits	30,457	2,808
Securities available for sale, at fair value	0	0
Held-to-maturity Securities	0
Other investments	0	0
Loans Held for sale, Amount	0	0
Loans and Leases Receivable, Net of Deferred Income	0	0
Deposits	0	0
Short-term borrowings	0	0
Subordinated debt	0	0
Long-term debt	0	0
Estimate of Fair Value Measurement [Member] | Level 2 [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	0	0
Interest-bearing deposits	0	0
Securities available for sale, at fair value	819,940	848,732
Held-to-maturity Securities	414,770
Other investments	58,087	62,952
Loans Held for sale, Amount	11,613	5,763
Loans and Leases Receivable, Net of Deferred Income	30,774	30,979
Deposits	4,395,297	4,198,817
Short-term borrowings	1,464,408	1,510,718
Subordinated debt	0	0
Long-term debt	10,077	9,834
Estimate of Fair Value Measurement [Member] | Level 3 [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Cash and due from banks	0	0
Interest-bearing deposits	0	0
Securities available for sale, at fair value	35,393	37,828
Held-to-maturity Securities	0
Other investments	0	0
Loans Held for sale, Amount	0	0
Loans and Leases Receivable, Net of Deferred Income	4,826,353	4,659,873
Deposits	0	0
Short-term borrowings	0	0
Subordinated debt	61,427	62,794
Long-term debt	$ 0	$ 0