Fair Value Measurements - Balances and Levels of Assets Measured at Fair Value on Recurring and Nonrecurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2014
Financial assets:
Available-for-sale securities, at fair value	$ 553,357		$ 649,387
Foreclosed real estate, net	8,964	$ 9,902	11,641	$ 11,547	$ 6,199	$ 7,259
Mortgage servicing rights estimated fair value	32,600
Impaired loans	14,367		15,576
Fair Value, Measurements, Recurring
Financial assets:
Available-for-sale securities, at fair value	553,357		649,387
Loans held for sale	486,601		273,196
Derivative assets	16,811		6,023
Financial liabilities:
Derivative liabilities	4,807		369
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Financial assets:
Available-for-sale securities, at fair value	548,808		644,531
Loans held for sale	486,601		273,196
Derivative assets	16,811		6,023
Financial liabilities:
Derivative liabilities	4,807		369
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Financial assets:
Available-for-sale securities, at fair value	4,549		4,856
Fair Value, Measurements, Recurring | U.S. Government Agency Securities
Financial assets:
Available-for-sale securities, at fair value	2,501		33,808
Fair Value, Measurements, Recurring | U.S. Government Agency Securities | Significant Other Observable Inputs (Level 2)
Financial assets:
Available-for-sale securities, at fair value	2,501		33,808
Fair Value, Measurements, Recurring | Mortgage-backed Securities
Financial assets:
Available-for-sale securities, at fair value	433,564		522,373
Fair Value, Measurements, Recurring | Mortgage-backed Securities | Significant Other Observable Inputs (Level 2)
Financial assets:
Available-for-sale securities, at fair value	433,564		522,373
Fair Value, Measurements, Recurring | Municipals, Tax Exempt
Financial assets:
Available-for-sale securities, at fair value	104,112		79,837
Fair Value, Measurements, Recurring | Municipals, Tax Exempt | Significant Other Observable Inputs (Level 2)
Financial assets:
Available-for-sale securities, at fair value	104,112		79,837
Fair Value, Measurements, Recurring | Treasury Securities
Financial assets:
Available-for-sale securities, at fair value	4,506		4,485
Fair Value, Measurements, Recurring | Treasury Securities | Significant Other Observable Inputs (Level 2)
Financial assets:
Available-for-sale securities, at fair value	4,506		4,485
Fair Value, Measurements, Recurring | Equity Securities
Financial assets:
Available-for-sale securities, at fair value	8,674		8,884
Fair Value, Measurements, Recurring | Equity Securities | Significant Other Observable Inputs (Level 2)
Financial assets:
Available-for-sale securities, at fair value	4,125		4,028
Fair Value, Measurements, Recurring | Equity Securities | Significant Unobservable Inputs (Level 3)
Financial assets:
Available-for-sale securities, at fair value	4,549		4,856
Fair Value, Measurements, Nonrecurring
Financial assets:
Foreclosed real estate, net	2,564		6,275
Mortgage servicing rights estimated fair value	46,291
Impaired loans	2,968		29,135
Fair Value, Measurements, Nonrecurring | Commercial and Industrial
Financial assets:
Impaired loans	362		2,007
Fair Value, Measurements, Nonrecurring | Consumer and Other
Financial assets:
Impaired loans	4		4
Fair Value, Measurements, Nonrecurring | Owner Occupied | Commercial Real Estate
Financial assets:
Impaired loans	825		6,493
Fair Value, Measurements, Nonrecurring | Non-Owner Occupied | Commercial Real Estate
Financial assets:
Impaired loans	1,352		7,572
Fair Value, Measurements, Nonrecurring | 1-to-4 Family Mortgage | Residential Real Estate
Financial assets:
Impaired loans	110		6,127
Fair Value, Measurements, Nonrecurring | Residential Line of Credit | Residential Real Estate
Financial assets:
Impaired loans	315
Fair Value, Measurements, Nonrecurring | Construction Loans | Commercial Real Estate
Financial assets:
Impaired loans			6,896
Fair Value, Measurements, Nonrecurring | Multi-Family Mortgage | Residential Real Estate
Financial assets:
Impaired loans			36
Fair Value, Measurements, Nonrecurring | Significant Unobservable Inputs (Level 3)
Financial assets:
Foreclosed real estate, net	2,564		6,275
Mortgage servicing rights estimated fair value	46,291
Impaired loans	2,968		29,135
Fair Value, Measurements, Nonrecurring | Significant Unobservable Inputs (Level 3) | Commercial and Industrial
Financial assets:
Impaired loans	362		2,007
Fair Value, Measurements, Nonrecurring | Significant Unobservable Inputs (Level 3) | Consumer and Other
Financial assets:
Impaired loans	4		4
Fair Value, Measurements, Nonrecurring | Significant Unobservable Inputs (Level 3) | Owner Occupied | Commercial Real Estate
Financial assets:
Impaired loans	825		6,493
Fair Value, Measurements, Nonrecurring | Significant Unobservable Inputs (Level 3) | Non-Owner Occupied | Commercial Real Estate
Financial assets:
Impaired loans	1,352		7,572
Fair Value, Measurements, Nonrecurring | Significant Unobservable Inputs (Level 3) | 1-to-4 Family Mortgage | Residential Real Estate
Financial assets:
Impaired loans	110		6,127
Fair Value, Measurements, Nonrecurring | Significant Unobservable Inputs (Level 3) | Residential Line of Credit | Residential Real Estate
Financial assets:
Impaired loans	$ 315
Fair Value, Measurements, Nonrecurring | Significant Unobservable Inputs (Level 3) | Construction Loans | Commercial Real Estate
Financial assets:
Impaired loans			6,896
Fair Value, Measurements, Nonrecurring | Significant Unobservable Inputs (Level 3) | Multi-Family Mortgage | Residential Real Estate
Financial assets:
Impaired loans			$ 36