Fair Value Measurements - Carrying Values and Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands		Sep. 30, 2018	Dec. 31, 2017
ASSETS
Securities, at fair value		$ 682,535	$ 698,291
Portfolio loans, net		5,747,251	5,705,059
FHLB and other restricted stock		31,178	29,270
Carrying Value
ASSETS
Cash and due from banks, including interest-bearing deposits	[1]	132,650	117,152
Securities, at fair value	[1]	682,535	698,291
Loans held for sale	[1]	4,207	4,485
Portfolio loans, net	[1]	5,747,251	5,705,059
Bank owned life insurance	[1]	73,626	72,150
FHLB and other restricted stock	[1]	31,178	29,270
Trading securities held in a Rabbi Trust	[1]	5,377	5,080
Mortgage servicing rights	[1]	4,421	4,133
LIABILITIES
Deposits	[1]	5,467,509	5,427,891
Securities sold under repurchase agreements	[1]	45,200	50,161
Short-term borrowings	[1]	535,000	540,000
Long-term borrowings	[1]	45,434	47,301
Junior subordinated debt securities	[1]	45,619	45,619
Carrying Value | Interest rate swaps
ASSETS
Derivative financial assets	[1]	7,448	3,074
LIABILITIES
Derivative financial liabilities	[1]	7,483	3,055
Carrying Value | Interest rate lock commitments
ASSETS
Derivative financial assets	[1]	229	226
Carrying Value | Forward sale contracts—mortgage loans
ASSETS
Derivative financial assets	[1]	61
LIABILITIES
Derivative financial liabilities	[1]		5
Fair Value Measurements
ASSETS
Cash and due from banks, including interest-bearing deposits		132,650	117,152
Securities, at fair value		682,535	698,291
Loans held for sale		4,377	4,583
Portfolio loans, net		5,585,934	5,690,292
Bank owned life insurance		73,626	72,150
FHLB and other restricted stock		31,178	29,270
Trading securities held in a Rabbi Trust		5,377	5,080
Mortgage servicing rights		5,456	4,571
LIABILITIES
Deposits		5,451,776	5,426,928
Securities sold under repurchase agreements		45,200	50,161
Short-term borrowings		535,000	540,000
Long-term borrowings		45,564	47,618
Junior subordinated debt securities		45,619	45,619
Fair Value Measurements | Interest rate swaps
ASSETS
Derivative financial assets		7,448	3,074
LIABILITIES
Derivative financial liabilities		7,483	3,055
Fair Value Measurements | Interest rate lock commitments
ASSETS
Derivative financial assets		229	226
Fair Value Measurements | Forward sale contracts—mortgage loans
ASSETS
Derivative financial assets		61
LIABILITIES
Derivative financial liabilities			5
Fair Value Measurements | Level 1
ASSETS
Cash and due from banks, including interest-bearing deposits		132,650	117,152
Securities, at fair value		0	0
Loans held for sale		0	0
Portfolio loans, net		0	0
Bank owned life insurance		0	0
FHLB and other restricted stock		0	0
Trading securities held in a Rabbi Trust		5,377	5,080
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—mortgage loans
ASSETS
Derivative financial assets		0
LIABILITIES
Derivative financial liabilities			0
Fair Value Measurements | Level 2
ASSETS
Cash and due from banks, including interest-bearing deposits		0	0
Securities, at fair value		682,535	698,291
Loans held for sale		0	0
Portfolio loans, net		0	0
Bank owned life insurance		73,626	72,150
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		7,448	3,074
LIABILITIES
Derivative financial liabilities		7,483	3,055
Fair Value Measurements | Level 2 | Interest rate lock commitments
ASSETS
Derivative financial assets		229	226
Fair Value Measurements | Level 2 | Forward sale contracts—mortgage loans
ASSETS
Derivative financial assets		61
LIABILITIES
Derivative financial liabilities			5
Fair Value Measurements | Level 3
ASSETS
Cash and due from banks, including interest-bearing deposits		0	0
Securities, at fair value		0	0
Loans held for sale		4,377	4,583
Portfolio loans, net		5,585,934	5,690,292
Bank owned life insurance		0	0
FHLB and other restricted stock		31,178	29,270
Trading securities held in a Rabbi Trust		0	0
Mortgage servicing rights		5,456	4,571
LIABILITIES
Deposits		5,451,776	5,426,928
Securities sold under repurchase agreements		45,200	50,161
Short-term borrowings		535,000	540,000
Long-term borrowings		45,564	47,618
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—mortgage loans
ASSETS
Derivative financial assets		$ 0
LIABILITIES
Derivative financial liabilities			$ 0

[1] As reported in the Consolidated Balance Sheets