Summary of Significant Accounting Policies, Goodwill and Intangible Assets (Details) $ in Millions	12 Months Ended
Dec. 31, 2018 USD ($) segment item	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Summary of Significant Accounting Policies
Number of reporting units \| item	2
Number of reportable business segments \| segment	2
Goodwill impairment	$ 0.0	$ 0.0	$ 0.0
Impairment of intangible assets	$ 0.0	$ 0.0	$ 0.0

No definition available.

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Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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The amount of impairment loss recognized in the period resulting from the write-down of the carrying amount of an intangible asset (excluding goodwill) to fair value.

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Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

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Number of reporting units tested for impairment of goodwill. A reporting unit is an operating segment or one level below an operating segment.

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No definition available.

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