Summary of Significant Accounting Policies - Recently issued pronouncements (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Jan. 01, 2019
Recently Issued Pronouncement
Original expected duration	true
Underlying contract	true
ASU 2016-02 \| Minimum
Recently Issued Pronouncement
Right-of-use assets		$ 3.6
Operating leases liabilities		3.6
ASU 2016-02 \| Maximum
Recently Issued Pronouncement
Right-of-use assets		4.0
Operating leases liabilities		$ 4.0

No definition available.

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- Definition

Present value of lessee's discounted obligation for lease payments from operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (b)
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- Definition

Amount of lessee's right to use underlying asset under operating lease.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (a)
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- Definition

Indicates (true false) whether practical expedient was elected to recognize incremental cost of obtaining contract as expense when incurred if amortization period would have been one year or less.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 22
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Indicates (true false) whether practical expedient was elected not to disclose amount of transaction price allocated to remaining performance obligation and explanation of expected timing of revenue recognition for reporting period presented prior to date of initial application under retrospective method.

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