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Debt Securities Held-to-Maturity - Held-to-Maturity Securities in a Continuous Unrealized Loss Positions (Details)	3 Months Ended
	Mar. 31, 2019 USD ($) loan	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity securities sold	$ 0	$ 0
Held-to-maturity securities pledged to secure borrowings and deposits	6,400,000
Unrealized losses
Less than 12 months	0		$ 34,000
12 months or more	128,000		222,000
Total	128,000		256,000
Estimated fair value
Less than 12 months	0		2,133,000
12 months or more	9,320,000		7,116,000
Total	9,320,000		9,249,000
Other-than-temporary impairment charge recognized in earnings	0	$ 0
Mortgage Backed Securities Pass Through Certificates
Unrealized losses
Less than 12 months	0		34,000
12 months or more	128,000		222,000
Total	128,000		256,000
Estimated fair value
Less than 12 months	0		2,133,000
12 months or more	9,320,000		7,116,000
Total	$ 9,320,000		$ 9,249,000
Number of mortgage-backed securities in unrealized loss position, greater than 12 months (loan) | loan	6

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