Fair Value Measurements - Assets and Liabilities Not Measured and Reported at Fair Value on a Recurring Basis or Nonrecurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financial assets
Securities available for sale	$ 948,365	$ 671,488
Mortgage loans held for sale	204,472	108,316
Mortgage servicing rights	40,216	39,339
Carrying Value
Financial assets
Cash and cash equivalents	250,978	281,453
Securities available for sale	948,365	671,488
Mortgage loans held for sale	204,472	108,316
Loans, net	7,651,669	7,574,111
Mortgage servicing rights	40,216	39,339
Derivative instruments	9,311	5,977
Financial liabilities
Deposits	8,357,769	7,921,075
Short-term borrowings	57,753	89,814
Other long-term borrowings	86	98
Federal Home Loan Bank advances	7,276	7,493
Junior subordinated debentures	86,018	85,881
Subordinated notes	114,059	114,074
Derivative instruments	5,950	6,039
Fair Value
Financial assets
Cash and cash equivalents	250,978	281,453
Securities available for sale	948,365	671,488
Mortgage loans held for sale	204,472	108,316
Loans, net	7,482,089	7,514,185
Mortgage servicing rights	53,426	47,868
Derivative instruments	9,311	5,977
Financial liabilities
Deposits	8,347,898	7,923,476
Short-term borrowings	57,753	89,814
Other long-term borrowings	86	98
Federal Home Loan Bank advances	7,362	7,661
Junior subordinated debentures	77,692	69,702
Subordinated notes	116,763	118,650
Derivative instruments	5,950	6,039
Fair Value | Level 1
Financial assets
Cash and cash equivalents	250,978	281,453
Securities available for sale	0	0
Mortgage loans held for sale	0	0
Loans, net	0	0
Mortgage servicing rights	0	0
Derivative instruments	0	0
Financial liabilities
Deposits	6,504,003	6,114,391
Short-term borrowings	57,753	89,814
Other long-term borrowings	86	98
Federal Home Loan Bank advances	0	0
Junior subordinated debentures	0	0
Subordinated notes	0	0
Derivative instruments	0	0
Fair Value | Level 2
Financial assets
Cash and cash equivalents	0	0
Securities available for sale	938,320	662,100
Mortgage loans held for sale	204,472	108,316
Loans, net	0	0
Mortgage servicing rights	0	0
Derivative instruments	9,311	5,977
Financial liabilities
Deposits	1,843,895	1,809,085
Short-term borrowings	0	0
Other long-term borrowings	0	0
Federal Home Loan Bank advances	7,362	7,661
Junior subordinated debentures	77,692	69,702
Subordinated notes	116,763	118,650
Derivative instruments	5,950	6,039
Fair Value | Level 3
Financial assets
Cash and cash equivalents	0	0
Securities available for sale	10,045	9,388
Mortgage loans held for sale	0	0
Loans, net	7,482,089	7,514,185
Mortgage servicing rights	53,426	47,868
Derivative instruments	0	0
Financial liabilities
Deposits	0	0
Short-term borrowings	0	0
Other long-term borrowings	0	0
Federal Home Loan Bank advances	0	0
Junior subordinated debentures	0	0
Subordinated notes	0	0
Derivative instruments	$ 0	$ 0