Securities - Additional Information (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2017	Dec. 31, 2016
Repurchase Agreements
Securities Pledged
Amortized cost of securities pledged	$ 6.6	$ 12.2
Securities pledged and available to be sold under repurchase agreements, fair value	6.6	12.2
Derivative
Securities Pledged
Amortized cost of securities pledged	3.4	5.2
Securities pledged and available to be sold under repurchase agreements, fair value	3.3	5.2
Securities pledged to various Federal Reserve Districts relating to deposits of bankruptcy trustees
Securities Pledged
Amortized cost of securities	52.4	73.0
Fair value of pledged securities	$ 52.4	72.6
Public Deposits
Securities Pledged
Amortized cost of securities		$ 1.3

Amortized Cost of Securities Pledged to Various Federal Reserve Districts.

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- Definition

Fair Value of Securities Pledged to Various Federal Reserve Districts.

+ References

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- Definition

Amortized Cost of financial instrument held by the entity.

+ References

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- Definition

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+ References

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- Definition

Fair value of financial instrument held by the entity for its own account (proprietary securities) for trading or investment purposes that are carried at fair value and pledged to counterparties as collateral for financing transactions.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (b)(1)(i)
-URI http://asc.fasb.org/extlink&oid=64858031&loc=SL6224234-111729

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66007379&loc=d3e113888-111728

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