Fair Value Measurements - Carrying Values and Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
ASSETS
Securities	$ 870,121	$ 773,693
Portfolio loans, net	6,861,739	7,108,248
LIABILITIES
Junior subordinated debt securities	64,128	64,083
Carrying Value
ASSETS
Cash and due from banks, including interest-bearing deposits	934,377	229,666
Securities	870,121	773,693
Loans held for sale	4,303	18,528
Portfolio loans, net	6,897,715	7,108,248
Collateral receivable	43,193	77,936
Securities held in a deferred compensation plan	9,320	6,794
Mortgage servicing rights	7,015	4,976
LIABILITIES
Deposits	7,945,119	7,420,538
Securities sold under repurchase agreements	72,586	65,163
Short-term borrowings	0	75,000
Long-term borrowings	22,693	23,681
Junior subordinated debt securities	64,128	64,083
Carrying Value | Interest rate swaps
ASSETS
Derivative financial assets	42,177	78,319
LIABILITIES
Derivative financial liabilities	42,554	79,033
Carrying Value | Interest rate lock commitments
ASSETS
Derivative financial assets	813	2,900
Carrying Value | Forward sale contracts
ASSETS
Derivative financial assets	101
LIABILITIES
Derivative financial liabilities		385
Fair Value Measurements
ASSETS
Cash and due from banks, including interest-bearing deposits	934,377	229,666
Securities	870,121	773,693
Loans held for sale	4,303	18,528
Portfolio loans, net	6,784,028	7,028,446
Collateral receivable	43,193	77,936
Securities held in a deferred compensation plan	9,320	6,794
Mortgage servicing rights	7,015	4,976
LIABILITIES
Deposits	7,944,461	7,422,894
Securities sold under repurchase agreements	72,586	65,163
Short-term borrowings	0	75,000
Long-term borrowings	23,172	24,545
Junior subordinated debt securities	64,128	64,083
Fair Value Measurements | Interest rate swaps
ASSETS
Derivative financial assets	42,177	78,319
LIABILITIES
Derivative financial liabilities	42,554	79,033
Fair Value Measurements | Interest rate lock commitments
ASSETS
Derivative financial assets	813	2,900
Fair Value Measurements | Forward sale contracts
ASSETS
Derivative financial assets	101
LIABILITIES
Derivative financial liabilities		385
Fair Value Measurements | Level 1
ASSETS
Cash and due from banks, including interest-bearing deposits	934,377	229,666
Securities	86,351	13,510
Loans held for sale	0	0
Portfolio loans, net	0	0
Collateral receivable	43,193	77,936
Securities held in a deferred compensation plan	9,320	6,794
Mortgage servicing rights	0	0
LIABILITIES
Deposits	6,743,851	6,033,075
Securities sold under repurchase agreements	72,586	65,163
Short-term borrowings	0	75,000
Long-term borrowings	4,349	4,494
Junior subordinated debt securities	64,128	64,083
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
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	783,770	760,183
Loans held for sale	4,303	0
Portfolio loans, net	0	0
Collateral receivable	0	0
Securities held in a deferred compensation plan	0	0
Mortgage servicing rights	0	0
LIABILITIES
Deposits	1,200,610	1,389,819
Securities sold under repurchase agreements	0	0
Short-term borrowings	0	0
Long-term borrowings	18,823	20,051
Junior subordinated debt securities	0	0
Fair Value Measurements | Level 2 | Interest rate swaps
ASSETS
Derivative financial assets	42,177	78,319
LIABILITIES
Derivative financial liabilities	42,554	79,033
Fair Value Measurements | Level 2 | Interest rate lock commitments
ASSETS
Derivative financial assets	0	0
Fair Value Measurements | Level 2 | Forward sale contracts
ASSETS
Derivative financial assets	0
LIABILITIES
Derivative financial liabilities		385
Fair Value Measurements | Level 3
ASSETS
Cash and due from banks, including interest-bearing deposits	0	0
Securities	0	0
Loans held for sale	0	18,528
Portfolio loans, net	6,784,028	7,028,446
Collateral receivable	0	0
Securities held in a deferred compensation plan	0	0
Mortgage servicing rights	7,015	4,976
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 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	813	2,900
Fair Value Measurements | Level 3 | Forward sale contracts
ASSETS
Derivative financial assets	$ 101
LIABILITIES
Derivative financial liabilities		$ 0