Summary of Significant Accounting Policies (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) segment	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Property, Plant and Equipment [Line Items]
Number of reportable segments | segment	1
Required reserves on deposits maintained	$ 17.5	$ 18.2
Minimum period of consecutive contractual payments to no longer be considered in nonaccrual status	6 years
Removal of remaining clawback liability, FDIC loss share termination			$ 3.5
Removal of remaining FDIC receivable, FDIC loss share termination			$ 7.2
Finite-lived intangible assets useful life	10 years	10 years
Furniture, Fixtures and Equipment [Member] | Minimum
Property, Plant and Equipment [Line Items]
Property plant and equipment useful life	3 years
Furniture, Fixtures and Equipment [Member] | Maximum
Property, Plant and Equipment [Line Items]
Property plant and equipment useful life	10 years
Building and Leasehold Improvements [Member] | Minimum
Property, Plant and Equipment [Line Items]
Property plant and equipment useful life	10 years
Building and Leasehold Improvements [Member] | Maximum
Property, Plant and Equipment [Line Items]
Property plant and equipment useful life	40 years
Software [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment useful life	3 years
Core Deposits [Member]
Property, Plant and Equipment [Line Items]
Finite-lived intangible assets useful life	10 years
State and Local Jurisdiction [Member]
Property, Plant and Equipment [Line Items]
Right to receive state tax credit at agreed upon rates	10 years