Fair Value of Assets and Liabilities (Details 2) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2017 USD ($) Security	Dec. 31, 2017 USD ($) Security	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Breakdown of trust preferred securities
Number considered OTTI | Security	1
Life-to-date impairment recognized in earnings	$ 140				$ 140
Trust preferred securities
Breakdown of trust preferred securities
Total number of trust preferred securities | Security		2
Par value, trust preferred securities		$ 1,939
Number not considered OTTI | Security		1
Par value, trust preferred securities not considered OTTI		$ 903
Number considered OTTI | Security		1
Par value, trust preferred securities considered OTTI		$ 1,036
Life-to-date impairment recognized in earnings	$ 140	140	$ 140	$ 140	$ 140
Life-to-date impairment recognized in other comprehensive income		723
Total life-to-date impairment		$ 863