Significant Accounting Policies - Revenue Recognition (Details)	12 Months Ended
Dec. 31, 2018
Accounting Changes
Revenue, Practical Expedient, Incremental Cost of Obtaining Contract [true false]	true
Adjustments for adoption of guidance \| ASU 2014-09, Revenue from Contracts with Customers
Accounting Changes
Billing retention recognized at time of transfer of control (as a percent)	10.00%

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.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130569-203045

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 340
-SubTopic 40
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=68051541&loc=SL51790836-203054

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Balance Type:	na
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