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Fair Value Measurements - Narratives (Details) | 12 Months Ended
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Dec. 31, 2017 USD ($) Impaired_Asset_And_Liabilty | Dec. 31, 2016 USD ($) Impaired_Asset_And_Liabilty | Dec. 31, 2015 USD ($) Impaired_Asset_And_Liabilty
Fair Value Disclosures [Abstract] |  |  |
Fair value assets Level 1 to Level 2 transfers amount | $ 0 | $ 0 | $ 0
Fair value liabilities Level 1 to Level 2 transfers amount | 0 | 0 | 0
Fair value assets Level 2 to Level 1 transfers amount | 0 | 0 | 0
Fair value liabilities Level 2 to Level 1 transfers amount | $ 0 | $ 0 | $ 0
Number of non-financial assets and liabilities impaired | Impaired_Asset_And_Liabilty | 0 | 0 | 0

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Balance Type: | na
Period Type: | duration

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- Definition Amount of transfers of assets measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2. + References 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 + Details
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Balance Type: | credit
Period Type: | instant

X
- Definition Amount of transfers of assets measured on a recurring basis out of Level 2 of the fair value hierarchy into Level 1. + References 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 + Details
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- References No definition available. + Details
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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 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 + Details
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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 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 + Details
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