Fair Value - Narrative (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Assets, level 1 to level 2 transfers	$ 0	$ 0
Assets, level 2 to level 1 transfers	9,000,000	0
Liabilities, level 1 to level 2 transfers	0	0
Liabilities, level 2 to level 1 transfers	$ 0	$ 0

Amount of transfers of assets measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bb)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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- Definition

Amount of transfers of assets measured on a recurring basis out of Level 2 of the fair value hierarchy into Level 1.

+ References

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- References

No definition available.

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- Definition

Amount of transfers of liabilities measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2.

+ References

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- Definition

Amount of transfers of liabilities measured on a recurring basis out of Level 2 of the fair value hierarchy into Level 1.

+ References

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