Summary of Significant Accounting Policies (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) segment	Dec. 31, 2016 USD ($)
Property, Plant and Equipment [Line Items]
Reserve requirements for banking subsidiaries	$ 6,600	$ 6,600
Investment in qualified affordable housing projects	$ 1,400	2,000
Number of reportable business segments | segment	3
Retained Earnings
Property, Plant and Equipment [Line Items]
Reclassification due to the adoption of ASU No. 2018-02		9,958
Minimum | Core deposit intangible
Property, Plant and Equipment [Line Items]
Amortization period for other intangible assets (in years)	5 years
Minimum | Covenants Noncompete
Property, Plant and Equipment [Line Items]
Amortization period for other intangible assets (in years)	3 years
Minimum | Customer relationships
Property, Plant and Equipment [Line Items]
Amortization period for other intangible assets (in years)	6 years
Maximum | Core deposit intangible
Property, Plant and Equipment [Line Items]
Amortization period for other intangible assets (in years)	10 years
Maximum | Covenants Noncompete
Property, Plant and Equipment [Line Items]
Amortization period for other intangible assets (in years)	6 years
Maximum | Customer relationships
Property, Plant and Equipment [Line Items]
Amortization period for other intangible assets (in years)	15 years
Building | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful (in years)	10 years
Building | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful (in years)	39 years
Furniture, fixtures, and equipment | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful (in years)	2 years
Furniture, fixtures, and equipment | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful (in years)	20 years
Accounting Standards Update 2018-02 | Early adoption effect
Property, Plant and Equipment [Line Items]
Reclassification due to the adoption of ASU No. 2018-02		$ 10,000