Fair Value Measurements - Balances and Levels of Assets Measured at Fair Value on Recurring and Nonrecurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015
Financial assets:
Available-for-sale securities, at fair value	$ 553,357		$ 582,183
Mortgage servicing rights, net	48,464	$ 47,593	33,081	$ 40,382	$ 36,611	$ 29,711
Foreclosed real estate, net	6,370	$ 6,811	7,403	$ 9,902	$ 10,533	$ 11,641
Impaired loans	9,214		12,951
Fair Value, Measurements, Recurring
Financial assets:
Available-for-sale securities, at fair value	553,357		582,183
Loans held for sale	427,416		507,442
Mortgage servicing rights, net	48,464
Derivatives assets	10,891		19,745
Financial liabilities:
Derivatives liabilities	1,350		586
Fair Value, Measurements, Recurring | U.S. Government Agency Securities
Financial assets:
Available-for-sale securities, at fair value	990		985
Fair Value, Measurements, Recurring | Mortgage-backed Securities
Financial assets:
Available-for-sale securities, at fair value	410,708		443,908
Fair Value, Measurements, Recurring | Municipals, Tax Exempt
Financial assets:
Available-for-sale securities, at fair value	122,698		116,923
Fair Value, Measurements, Recurring | Treasury Securities
Financial assets:
Available-for-sale securities, at fair value	10,310		11,757
Fair Value, Measurements, Recurring | Equity Securities
Financial assets:
Available-for-sale securities, at fair value	8,651		8,610
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Financial assets:
Available-for-sale securities, at fair value	548,808		577,634
Loans held for sale	427,416		507,442
Derivatives assets	10,891		19,745
Financial liabilities:
Derivatives liabilities	1,350		586
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | U.S. Government Agency Securities
Financial assets:
Available-for-sale securities, at fair value	990		985
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Mortgage-backed Securities
Financial assets:
Available-for-sale securities, at fair value	410,708		443,908
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Municipals, Tax Exempt
Financial assets:
Available-for-sale securities, at fair value	122,698		116,923
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Treasury Securities
Financial assets:
Available-for-sale securities, at fair value	10,310		11,757
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Equity Securities
Financial assets:
Available-for-sale securities, at fair value	4,102		4,061
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Financial assets:
Available-for-sale securities, at fair value	4,549		4,549
Mortgage servicing rights, net	48,464
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Equity Securities
Financial assets:
Available-for-sale securities, at fair value	4,549		4,549
Fair Value, Measurements, Nonrecurring
Financial assets:
Mortgage servicing rights, net			32,070
Foreclosed real estate, net	1,434		2,315
Impaired loans	518		1,281
Fair Value, Measurements, Nonrecurring | Commercial and Industrial
Financial assets:
Impaired loans	367		542
Fair Value, Measurements, Nonrecurring | Consumer and Other
Financial assets:
Impaired loans			1
Fair Value, Measurements, Nonrecurring | Non-Owner Occupied | Commercial Real Estate
Financial assets:
Impaired loans	151
Fair Value, Measurements, Nonrecurring | Owner Occupied | Commercial Real Estate
Financial assets:
Impaired loans			635
Fair Value, Measurements, Nonrecurring | 1-to-4 Family Mortgage | Residential Real Estate
Financial assets:
Impaired loans			103
Fair Value, Measurements, Nonrecurring | Significant Unobservable Inputs (Level 3)
Financial assets:
Mortgage servicing rights, net			32,070
Foreclosed real estate, net	1,434		2,315
Impaired loans	518		1,281
Fair Value, Measurements, Nonrecurring | Significant Unobservable Inputs (Level 3) | Commercial and Industrial
Financial assets:
Impaired loans	367		542
Fair Value, Measurements, Nonrecurring | Significant Unobservable Inputs (Level 3) | Consumer and Other
Financial assets:
Impaired loans			1
Fair Value, Measurements, Nonrecurring | Significant Unobservable Inputs (Level 3) | Non-Owner Occupied | Commercial Real Estate
Financial assets:
Impaired loans	$ 151
Fair Value, Measurements, Nonrecurring | Significant Unobservable Inputs (Level 3) | Owner Occupied | Commercial Real Estate
Financial assets:
Impaired loans			635
Fair Value, Measurements, Nonrecurring | Significant Unobservable Inputs (Level 3) | 1-to-4 Family Mortgage | Residential Real Estate
Financial assets:
Impaired loans			$ 103