Derivative Instruments - Narrative (Details) - USD ($)	3 Months Ended
Mar. 31, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Expected contract term	10 years
Maximum exposure	$ 250,000
Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of collateral	$ 13,174,000	$ 15,584,000

Fixed indexed annuities term.

No definition available.

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- Definition

Maximum amount of loss due to credit risk that, based on the gross fair value of the financial instrument, the entity would incur if parties to the financial instruments that make up the concentration failed completely to perform according to the terms of the contracts and the collateral or other security, if any, for the amount due proved to be of no value to the entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13537-108611

+ Details

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Balance Type:	debit
Period Type:	duration

- Definition

Fair value of securities received as collateral against derivative assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=82849420&loc=SL20226013-175313

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Details

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