Fair Value Measurement - Carrying Values and Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands		Sep. 30, 2016	Dec. 31, 2015
ASSETS
Securities available-for-sale		$ 671,128	$ 660,963
FHLB and other restricted stock		28,331	23,032
LIABILITIES
Junior subordinated debt securities		45,619	45,619
Carrying Value
ASSETS
Cash and due from banks, including interest-bearing deposits	[1]	125,163	99,399
Securities available-for-sale	[1]	671,128	660,963
Loans held for sale	[1]	11,695	35,321
Portfolio loans, net of unearned income	[1]	5,418,234	5,027,612
Bank owned life insurance	[1]	71,523	70,175
FHLB and other restricted stock	[1]	28,331	23,032
Trading securities held in a Rabbi Trust	[1]	4,312	4,021
Mortgage servicing rights	[1]	3,252	3,237
LIABILITIES
Deposits	[1]	5,145,431	4,876,611
Securities sold under repurchase agreements	[1]	40,949	62,086
Short-term borrowings	[1]	565,000	356,000
Long-term borrowings	[1]	15,303	117,043
Junior subordinated debt securities	[1]	45,619	45,619
Carrying Value | Interest Rate Swaps
ASSETS
Derivative financial assets	[1]	15,255	11,295
LIABILITIES
Derivative financial liabilities	[1]	15,202	11,276
Carrying Value | Interest Rate Lock Commitments
ASSETS
Derivative financial assets	[1]	739	261
Carrying Value | Forward Sale Contracts
LIABILITIES
Derivative financial liabilities	[1]	98	5
Fair Value Measurements
ASSETS
Cash and due from banks, including interest-bearing deposits		125,163	99,399
Securities available-for-sale		671,128	660,963
Loans held for sale		12,176	35,500
Portfolio loans, net of unearned income		5,406,298	5,001,004
Bank owned life insurance		71,523	70,175
FHLB and other restricted stock		28,331	23,032
Trading securities held in a Rabbi Trust		4,312	4,021
Mortgage servicing rights		3,253	3,396
LIABILITIES
Deposits		5,151,031	4,881,718
Securities sold under repurchase agreements		40,949	62,086
Short-term borrowings		565,000	356,000
Long-term borrowings		16,111	117,859
Junior subordinated debt securities		45,619	45,619
Fair Value Measurements | Interest Rate Swaps
ASSETS
Derivative financial assets		15,255	11,295
LIABILITIES
Derivative financial liabilities		15,202	11,276
Fair Value Measurements | Interest Rate Lock Commitments
ASSETS
Derivative financial assets		739	261
Fair Value Measurements | Forward Sale Contracts
LIABILITIES
Derivative financial liabilities		98	5
Fair Value Measurements | Level 1
ASSETS
Cash and due from banks, including interest-bearing deposits		125,163	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		4,312	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		671,128	660,963
Loans held for sale		0	0
Portfolio loans, net of unearned income		0	0
Bank owned life insurance		71,523	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		15,255	11,295
LIABILITIES
Derivative financial liabilities		15,202	11,276
Fair Value Measurements | Level 2 | Interest Rate Lock Commitments
ASSETS
Derivative financial assets		739	261
Fair Value Measurements | Level 2 | Forward Sale Contracts
LIABILITIES
Derivative financial liabilities		98	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		12,176	35,500
Portfolio loans, net of unearned income		5,406,298	5,001,004
Bank owned life insurance		0	0
FHLB and other restricted stock		28,331	23,032
Trading securities held in a Rabbi Trust		0	0
Mortgage servicing rights		3,253	3,396
LIABILITIES
Deposits		5,151,031	4,881,718
Securities sold under repurchase agreements		40,949	62,086
Short-term borrowings		565,000	356,000
Long-term borrowings		16,111	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.