Fair Value Measurement - Carrying Values and Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands		Mar. 31, 2016	Dec. 31, 2015
ASSETS
Securities available-for-sale		$ 677,221	$ 660,963
FHLB and other restricted stock		23,337	23,032
LIABILITIES
Junior subordinated debt securities		45,619	45,619
Carrying Value
ASSETS
Cash and due from banks, including interest-bearing deposits	[1]	121,669	99,399
Securities available-for-sale	[1]	677,221	660,963
Loans held for sale	[1]	11,739	35,321
Portfolio loans, net of unearned income	[1]	5,176,748	5,027,612
Bank owned life insurance	[1]	70,684	70,175
FHLB and other restricted stock	[1]	23,337	23,032
Trading securities held in a Rabbi Trust	[1]	4,069	4,021
Mortgage servicing rights	[1]	3,112	3,237
LIABILITIES
Deposits	[1]	5,017,925	4,876,611
Securities sold under repurchase agreements	[1]	60,025	62,086
Short-term borrowings	[1]	355,000	356,000
Long-term borrowings	[1]	116,468	117,043
Junior subordinated debt securities	[1]	45,619	45,619
Carrying Value | Interest Rate Swaps
ASSETS
Derivative financial assets	[1]	15,281	11,295
LIABILITIES
Derivative financial liabilities	[1]	15,165	11,276
Carrying Value | Interest Rate Lock Commitments
ASSETS
Derivative financial assets	[1]	526	261
Carrying Value | Forward Sale Contracts
LIABILITIES
Derivative financial liabilities	[1]	72	5
Fair Value Measurements
ASSETS
Cash and due from banks, including interest-bearing deposits		121,669	99,399
Securities available-for-sale		677,221	660,963
Loans held for sale		12,116	35,500
Portfolio loans, net of unearned income		5,163,461	5,001,004
Bank owned life insurance		70,684	70,175
FHLB and other restricted stock		23,337	23,032
Trading securities held in a Rabbi Trust		4,069	4,021
Mortgage servicing rights		3,112	3,396
LIABILITIES
Deposits		5,025,397	4,881,718
Securities sold under repurchase agreements		60,025	62,086
Short-term borrowings		355,000	356,000
Long-term borrowings		117,429	117,859
Junior subordinated debt securities		45,619	45,619
Fair Value Measurements | Interest Rate Swaps
ASSETS
Derivative financial assets		15,281	11,295
LIABILITIES
Derivative financial liabilities		15,165	11,276
Fair Value Measurements | Interest Rate Lock Commitments
ASSETS
Derivative financial assets		526	261
Fair Value Measurements | Forward Sale Contracts
LIABILITIES
Derivative financial liabilities		72	5
Fair Value Measurements | Level 1
ASSETS
Cash and due from banks, including interest-bearing deposits		121,669	99,399
Securities available-for-sale		0	0
Loans held for sale		0	0
Portfolio loans, net of unearned income		0	0
Bank owned life insurance		0	0
FHLB and other restricted stock		0	0
Trading securities held in a Rabbi Trust		4,069	4,021
Mortgage servicing rights		0	0
LIABILITIES
Deposits		0	0
Securities sold under repurchase agreements		0	0
Short-term borrowings		0	0
Long-term borrowings		0	0
Junior subordinated debt securities		0	0
Fair Value Measurements | Level 1 | Interest Rate Swaps
ASSETS
Derivative financial assets		0	0
LIABILITIES
Derivative financial liabilities		0	0
Fair Value Measurements | Level 1 | Interest Rate Lock Commitments
ASSETS
Derivative financial assets		0	0
Fair Value Measurements | Level 1 | Forward Sale Contracts
LIABILITIES
Derivative financial liabilities		0	0
Fair Value Measurements | Level 2
ASSETS
Cash and due from banks, including interest-bearing deposits		0	0
Securities available-for-sale		677,221	660,963
Loans held for sale		0	0
Portfolio loans, net of unearned income		0	0
Bank owned life insurance		70,684	70,175
FHLB and other restricted stock		0	0
Trading securities held in a Rabbi Trust		0	0
Mortgage servicing rights		0	0
LIABILITIES
Deposits		0	0
Securities sold under repurchase agreements		0	0
Short-term borrowings		0	0
Long-term borrowings		0	0
Junior subordinated debt securities		0	0
Fair Value Measurements | Level 2 | Interest Rate Swaps
ASSETS
Derivative financial assets		15,281	11,295
LIABILITIES
Derivative financial liabilities		15,165	11,276
Fair Value Measurements | Level 2 | Interest Rate Lock Commitments
ASSETS
Derivative financial assets		526	261
Fair Value Measurements | Level 2 | Forward Sale Contracts
LIABILITIES
Derivative financial liabilities		72	5
Fair Value Measurements | Level 3
ASSETS
Cash and due from banks, including interest-bearing deposits		0	0
Securities available-for-sale		0	0
Loans held for sale		12,116	35,500
Portfolio loans, net of unearned income		5,163,461	5,001,004
Bank owned life insurance		0	0
FHLB and other restricted stock		23,337	23,032
Trading securities held in a Rabbi Trust		0	0
Mortgage servicing rights		3,112	3,396
LIABILITIES
Deposits		5,025,397	4,881,718
Securities sold under repurchase agreements		60,025	62,086
Short-term borrowings		355,000	356,000
Long-term borrowings		117,429	117,859
Junior subordinated debt securities		45,619	45,619
Fair Value Measurements | Level 3 | Interest Rate Swaps
ASSETS
Derivative financial assets		0	0
LIABILITIES
Derivative financial liabilities		0	0
Fair Value Measurements | Level 3 | Interest Rate Lock Commitments
ASSETS
Derivative financial assets		0	0
Fair Value Measurements | Level 3 | Forward Sale Contracts
LIABILITIES
Derivative financial liabilities		$ 0	$ 0

[1] As reported in the Consolidated Balance Sheets.