Fair Value Measurements (Recurring Basis) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value	$ 3,021,832	$ 1,963,546
Carried at fair value		1,963,546
Loans held-for-sale	85,030	52,133
Loan servicing rights	71,013	63,841	$ 48,085	$ 0
Derivative assets	38,595	18,681
Total assets at fair value	3,216,470	2,098,201
Derivative liabilities	32,379	12,357
Total liabilities at fair value	32,379	12,357
Quoted Prices In Active Markets for Identical Assets (Level 1)
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value	0	0
Loans held-for-sale	0	0
Loan servicing rights	0	0
Derivative assets	0	0
Total assets at fair value	0	0
Derivative liabilities	0	0
Total liabilities at fair value	0	0
Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value	3,021,832	1,963,546
Loans held-for-sale	85,030	52,133
Loan servicing rights	0	0
Derivative assets	38,595	18,681
Total assets at fair value	3,145,457	2,034,360
Derivative liabilities	32,379	12,357
Total liabilities at fair value	32,379	12,357
Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value	0	0
Loans held-for-sale	0	0
Loan servicing rights	71,013	63,841
Derivative assets	0	0
Total assets at fair value	71,013	63,841
Derivative liabilities	0	0
Total liabilities at fair value	0	0
Customer-initiated derivatives
Summary of assets measured at fair value on a recurring basis
Derivative assets	26,680	9,376
Derivative liabilities	27,664	10,139
Customer-initiated derivatives | Quoted Prices In Active Markets for Identical Assets (Level 1)
Summary of assets measured at fair value on a recurring basis
Derivative assets	0	0
Derivative liabilities	0	0
Customer-initiated derivatives | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Derivative assets	26,680	9,376
Derivative liabilities	27,664	10,139
Customer-initiated derivatives | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Derivative assets	0	0
Derivative liabilities	0	0
Forward contracts related to mortgage loans to be delivered for sale
Summary of assets measured at fair value on a recurring basis
Derivative liabilities	719	34
Forward contracts related to mortgage loans to be delivered for sale | Quoted Prices In Active Markets for Identical Assets (Level 1)
Summary of assets measured at fair value on a recurring basis
Derivative liabilities	0	0
Forward contracts related to mortgage loans to be delivered for sale | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Derivative liabilities	719	34
Forward contracts related to mortgage loans to be delivered for sale | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Derivative liabilities	0	0
Interest rate lock commitments
Summary of assets measured at fair value on a recurring basis
Derivative assets	1,049	1,222
Interest rate lock commitments | Quoted Prices In Active Markets for Identical Assets (Level 1)
Summary of assets measured at fair value on a recurring basis
Derivative assets	0	0
Interest rate lock commitments | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Derivative assets	1,049	1,222
Interest rate lock commitments | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Derivative assets	0	0
Power Equity CD
Summary of assets measured at fair value on a recurring basis
Derivative assets	718	2,184
Derivative liabilities	718	2,184
Power Equity CD | Quoted Prices In Active Markets for Identical Assets (Level 1)
Summary of assets measured at fair value on a recurring basis
Derivative assets	0	0
Derivative liabilities	0	0
Power Equity CD | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Derivative assets	718	2,184
Derivative liabilities	718	2,184
Power Equity CD | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Derivative assets	0	0
Derivative liabilities	0	0
Risk management derivatives
Summary of assets measured at fair value on a recurring basis
Derivative assets	10,148	5,899
Derivative liabilities	3,278
Risk management derivatives | Quoted Prices In Active Markets for Identical Assets (Level 1)
Summary of assets measured at fair value on a recurring basis
Derivative assets	0	0
Derivative liabilities	0
Risk management derivatives | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Derivative assets	10,148	5,899
Derivative liabilities	3,278
Risk management derivatives | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Derivative assets	0	0
Derivative liabilities	0
Government and government-sponsored enterprises
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value	351,700	202,916
Government and government-sponsored enterprises | Quoted Prices In Active Markets for Identical Assets (Level 1)
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value	0	0
Government and government-sponsored enterprises | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value	351,700	202,916
Government and government-sponsored enterprises | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value	0	0
State and political subdivisions
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value	516,286	345,970
State and political subdivisions | Quoted Prices In Active Markets for Identical Assets (Level 1)
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value	0	0
State and political subdivisions | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value	516,286	345,970
State and political subdivisions | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value	0	0
Residential mortgage-backed securities
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value	213,428
Residential mortgage-backed securities | Quoted Prices In Active Markets for Identical Assets (Level 1)
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value	0
Residential mortgage-backed securities | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value	213,428
Residential mortgage-backed securities | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value	0
Residential mortgage-backed securities
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value		150,131
Residential mortgage-backed securities | Quoted Prices In Active Markets for Identical Assets (Level 1)
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value		0
Residential mortgage-backed securities | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value		150,131
Residential mortgage-backed securities | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value		0
Collateralized mortgage obligations
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value	1,601,298	1,033,845
Collateralized mortgage obligations | Quoted Prices In Active Markets for Identical Assets (Level 1)
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value	0	0
Collateralized mortgage obligations | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value	1,601,298	1,033,845
Collateralized mortgage obligations | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value	0	0
Corporate bonds
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value	293,063	192,794
Corporate bonds | Quoted Prices In Active Markets for Identical Assets (Level 1)
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value	0	0
Corporate bonds | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value	293,063	192,794
Corporate bonds | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value	0	0
Preferred stock
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value		1,824
Preferred stock | Quoted Prices In Active Markets for Identical Assets (Level 1)
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value		0
Preferred stock | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value		1,824
Preferred stock | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value		0
Trust preferred securities
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value	46,057	36,066
Trust preferred securities | Quoted Prices In Active Markets for Identical Assets (Level 1)
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value	0	0
Trust preferred securities | Significant Other Observable Inputs (Level 2)
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value	46,057	36,066
Trust preferred securities | Significant Unobservable Inputs (Level 3)
Summary of assets measured at fair value on a recurring basis
Total investment securities — carried at fair value	$ 0	$ 0