Fair Value - Valuation Methodology and Unobservable Inputs (Details) - Non-Recurring Basis - Significant Unobservable Inputs (Level 3) - Third Party Appraisals	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Impaired loans carried at fair value of collateral | Minimum
Fair value quantitative information
Adjustment for differences between the comparable sales (as a percent)	(16.00%)	(16.00%)
Impaired loans carried at fair value of collateral | Maximum
Fair value quantitative information
Adjustment for differences between the comparable sales (as a percent)	7.00%	7.00%
Impaired loans carried at fair value of collateral | Weighted Average
Fair value quantitative information
Adjustment for differences between the comparable sales (as a percent)	(3.00%)	(4.00%)
Real estate owned
Fair value quantitative information
Adjustment for differences between the comparable sales (as a percent)	(6.00%)	(6.00%)
Real estate owned | Weighted Average
Fair value quantitative information
Adjustment for differences between the comparable sales (as a percent)	(6.00%)	(6.00%)