Fair Value Measurement - Carrying Values and Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands		Sep. 30, 2017	Dec. 31, 2016
ASSETS
Securities available-for-sale		$ 697,954	$ 693,487
Portfolio loans, net of unearned income		5,820,758	5,611,419
FHLB and other restricted stock		33,120	31,817
LIABILITIES
Junior subordinated debt securities		45,619	45,619
Carrying Value
ASSETS
Cash and due from banks, including interest-bearing deposits	[1]	114,440	139,486
Securities available-for-sale	[1]	697,954	693,487
Loans held for sale	[1]	47,936	3,793
Portfolio loans, net of unearned income	[1]	5,820,758	5,611,419
Bank owned life insurance	[1]	71,639	72,081
FHLB and other restricted stock	[1]	33,120	31,817
Trading securities held in a Rabbi Trust	[1]	5,039	4,410
Mortgage servicing rights	[1]	3,992	3,744
LIABILITIES
Deposits	[1]	5,443,240	5,272,377
Securities sold under repurchase agreements	[1]	39,923	50,832
Short-term borrowings	[1]	685,000	660,000
Long-term borrowings	[1]	12,911	14,713
Junior subordinated debt securities	[1]	45,619	45,619
Carrying Value | Interest rate swap contracts - commercial loans
ASSETS
Derivative financial assets	[1]	4,814	6,960
LIABILITIES
Derivative financial liabilities	[1]	4,786	6,958
Carrying Value | Interest rate lock commitments - mortgage loans
ASSETS
Derivative financial assets	[1]	452	236
Carrying Value | Forward sale contracts - mortgage loans
LIABILITIES
Derivative financial liabilities	[1]	16	27
Fair Value Measurements
ASSETS
Cash and due from banks, including interest-bearing deposits		114,400	139,486
Securities available-for-sale		697,954	693,487
Loans held for sale		48,045	3,815
Portfolio loans, net of unearned income		5,758,326	5,551,266
Bank owned life insurance		71,639	72,081
FHLB and other restricted stock		33,120	31,817
Trading securities held in a Rabbi Trust		5,039	4,410
Mortgage servicing rights		4,286	4,098
LIABILITIES
Deposits		5,448,025	5,276,499
Securities sold under repurchase agreements		39,923	50,832
Short-term borrowings		685,000	660,000
Long-term borrowings		13,318	15,267
Junior subordinated debt securities		45,619	45,619
Fair Value Measurements | Interest rate swap contracts - commercial loans
ASSETS
Derivative financial assets		4,814	6,960
LIABILITIES
Derivative financial liabilities		4,786	6,958
Fair Value Measurements | Interest rate lock commitments - mortgage loans
ASSETS
Derivative financial assets		452	236
Fair Value Measurements | Forward sale contracts - mortgage loans
LIABILITIES
Derivative financial liabilities		16	27
Fair Value Measurements | Level 1
ASSETS
Cash and due from banks, including interest-bearing deposits		114,400	139,486
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		5,039	4,410
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 swap contracts - commercial loans
ASSETS
Derivative financial assets		0	0
LIABILITIES
Derivative financial liabilities		0	0
Fair Value Measurements | Level 1 | Interest rate lock commitments - mortgage loans
ASSETS
Derivative financial assets		0	0
Fair Value Measurements | Level 1 | Forward sale contracts - mortgage loans
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		697,954	693,487
Loans held for sale		0	0
Portfolio loans, net of unearned income		0	0
Bank owned life insurance		71,639	72,081
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 swap contracts - commercial loans
ASSETS
Derivative financial assets		4,814	6,960
LIABILITIES
Derivative financial liabilities		4,786	6,958
Fair Value Measurements | Level 2 | Interest rate lock commitments - mortgage loans
ASSETS
Derivative financial assets		452	236
Fair Value Measurements | Level 2 | Forward sale contracts - mortgage loans
LIABILITIES
Derivative financial liabilities		16	27
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		48,045	3,815
Portfolio loans, net of unearned income		5,758,326	5,551,266
Bank owned life insurance		0	0
FHLB and other restricted stock		33,120	31,817
Trading securities held in a Rabbi Trust		0	0
Mortgage servicing rights		4,286	4,098
LIABILITIES
Deposits		5,448,025	5,276,499
Securities sold under repurchase agreements		39,923	50,832
Short-term borrowings		685,000	660,000
Long-term borrowings		13,318	15,267
Junior subordinated debt securities		45,619	45,619
Fair Value Measurements | Level 3 | Interest rate swap contracts - commercial loans
ASSETS
Derivative financial assets		0	0
LIABILITIES
Derivative financial liabilities		0	0
Fair Value Measurements | Level 3 | Interest rate lock commitments - mortgage loans
ASSETS
Derivative financial assets		0	0
Fair Value Measurements | Level 3 | Forward sale contracts - mortgage loans
LIABILITIES
Derivative financial liabilities		$ 0	$ 0

[1] As reported in the Consolidated Balance Sheets.