Fair Value Measurements - Fair Value Inputs, Quantitative Information (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Impaired Loans | Minimum | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate of long-lived assets to be disposed of by sale	0.00%
Impaired Loans | Maximum | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate of long-lived assets to be disposed of by sale	66.00%
Impaired Loans | Weighted Average | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate of long-lived assets to be disposed of by sale	31.00%
Other Real Estate Owned | Minimum | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate of long-lived assets to be disposed of by sale	8.00%
Other Real Estate Owned | Maximum | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate of long-lived assets to be disposed of by sale	96.00%
Other Real Estate Owned | Weighted Average | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate of long-lived assets to be disposed of by sale	18.00%
Asses to be Disposed of by Sale | Minimum | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate of long-lived assets to be disposed of by sale	0.00%
Asses to be Disposed of by Sale | Maximum | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate of long-lived assets to be disposed of by sale	9.00%
Asses to be Disposed of by Sale | Weighted Average | Market Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate of long-lived assets to be disposed of by sale	6.00%
Carrying Amount
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Net loans held for investment	$ 7,427,815	$ 5,340,536
Change During Period | Fair Value Measured on a Non-recurring Basis
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value of long-lived assets to be disposed of by sale	209	1,028
Estimated Fair Value
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Net loans held for investment	7,163,825	5,248,127
Estimated Fair Value | Fair Value Measured on a Non-recurring Basis
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Impaired loans	34,489	39,344
Other real estate owned	1,578	2,110
Fair Value of long-lived assets to be disposed of by sale	356	1,335
Significant Unobservable Inputs (Level 3) | Fair Value Measured on a Non-recurring Basis
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Impaired loans	34,489	39,344
Other real estate owned	1,578	2,110
Fair Value of long-lived assets to be disposed of by sale	356	1,335
Significant Unobservable Inputs (Level 3) | Carrying Amount | Fair Value Measured on a Non-recurring Basis
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Impaired loans	58,523	65,238
Fair Value of long-lived assets to be disposed of by sale	565	2,363
Significant Unobservable Inputs (Level 3) | Estimated Fair Value
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Net loans held for investment		39,344
Impaired loans	34,489
Significant Unobservable Inputs (Level 3) | Estimated Fair Value | Fair Value Measured on a Non-recurring Basis
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Impaired loans	$ 34,489	$ 39,344