Fair Value Measurements - Carrying Values and Fair Values of Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013
ASSETS
Securities available-for-sale	$ 615,657		$ 509,425
FHLB and other restricted stock	18,995		13,629
LIABILITIES
Junior subordinated debt securities	45,619		45,619
Carrying Value [Member]
ASSETS
Cash and due from banks, including interest-bearing deposits	143,831	[1]	108,356	[1]
Securities available-for-sale	615,657	[1]	509,425	[1]
Loans held for sale	3,126	[1]	2,136	[1]
Portfolio loans, net of unearned income	3,801,189	[1]	3,566,199	[1]
Bank owned life insurance	61,794	[1]	60,480	[1]
FHLB and other restricted stock	18,995	[1]	13,629	[1]
Trading securities held in a Rabbi Trust	3,286	[1]	2,864	[1]
Mortgage servicing rights	2,792	[1]	2,919	[1]
LIABILITIES
Deposits	3,901,101	[1]	3,672,308	[1]
Securities sold under repurchase agreements	23,084	[1]	33,847	[1]
Short-term borrowings	265,000	[1]	140,000	[1]
Long-term borrowings	20,042	[1]	21,810	[1]
Junior subordinated debt securities	45,619	[1]	45,619	[1]
Carrying Value [Member] | Interest Rate Swaps [Member]
ASSETS
Derivative financial assets	12,125	[1]	13,698	[1]
LIABILITIES
Derivative financial liabilities	12,103	[1]	13,647	[1]
Carrying Value [Member] | Interest Rate Lock Commitments [Member]
ASSETS
Derivative financial assets	187	[1]	85	[1]
Carrying Value [Member] | Forward Sale Contracts [Member]
ASSETS
Derivative financial assets			34	[1]
LIABILITIES
Derivative financial liabilities	10	[1]
Fair Value Measurements [Member]
ASSETS
Cash and due from banks, including interest-bearing deposits	143,831		108,356
Securities available-for-sale	615,657		509,425
Loans held for sale	3,167		2,139
Portfolio loans, net of unearned income	3,764,172		3,538,072
Bank owned life insurance	61,794		60,480
FHLB and other restricted stock	18,995		13,629
Trading securities held in a Rabbi Trust	3,286		2,864
Mortgage servicing rights	2,977		3,143
LIABILITIES
Deposits	3,903,211		3,673,624
Securities sold under repurchase agreements	23,084		33,847
Short-term borrowings	265,000		140,000
Long-term borrowings	21,022		22,924
Junior subordinated debt securities	45,619		45,619
Fair Value Measurements [Member] | Level 1 [Member]
ASSETS
Cash and due from banks, including interest-bearing deposits	143,831		108,356
Securities available-for-sale	179		202
Trading securities held in a Rabbi Trust	3,286		2,864
Fair Value Measurements [Member] | Level 2 [Member]
ASSETS
Securities available-for-sale	615,478		509,223
Bank owned life insurance	61,794		60,480
Fair Value Measurements [Member] | Level 3 [Member]
ASSETS
Loans held for sale	3,167		2,139
Portfolio loans, net of unearned income	3,764,172		3,538,072
FHLB and other restricted stock	18,995		13,629
Mortgage servicing rights	2,977		3,143
LIABILITIES
Deposits	3,903,211		3,673,624
Securities sold under repurchase agreements	23,084		33,847
Short-term borrowings	265,000		140,000
Long-term borrowings	21,022		22,924
Junior subordinated debt securities	45,619		45,619
Fair Value Measurements [Member] | Interest Rate Swaps [Member]
ASSETS
Derivative financial assets	12,125		13,698
LIABILITIES
Derivative financial liabilities	12,103		13,647
Fair Value Measurements [Member] | Interest Rate Swaps [Member] | Level 2 [Member]
ASSETS
Derivative financial assets	12,125		13,698
LIABILITIES
Derivative financial liabilities	12,103		13,647
Fair Value Measurements [Member] | Interest Rate Lock Commitments [Member]
ASSETS
Derivative financial assets	187		85
Fair Value Measurements [Member] | Interest Rate Lock Commitments [Member] | Level 2 [Member]
ASSETS
Derivative financial assets	187		85
Fair Value Measurements [Member] | Forward Sale Contracts [Member]
ASSETS
Derivative financial assets			34
LIABILITIES
Derivative financial liabilities	10
Fair Value Measurements [Member] | Forward Sale Contracts [Member] | Level 2 [Member]
ASSETS
Derivative financial assets			34
LIABILITIES
Derivative financial liabilities	$ 10

[1] As reported in the Consolidated Balance Sheets.