Supplemental Consolidated Balance Sheet Information (Components of Other Non-Current Liabilities) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Balance Sheet Related Disclosures [Abstract]
Deferred acquisition liabilities - non-current	$ 733	$ 710
Deferred rent - non-current		21,648
Other non-current liabilities	3,588	2,919
Total other non-current liabilities	$ 4,321	$ 25,277

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Amount of liabilities due after one year or the normal operating cycle, if longer, assumed at the acquisition date.

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For a classified balance sheet, the cumulative difference between the rental income or payments required by a lease agreement and the rental income or expense recognized on a straight-line basis, or other systematic and rational basis more representative of the time pattern in which use or benefit is granted or derived from the leased property, expected to be recognized in income or expense, by the lessor or lessee, respectively, more than one year after the balance sheet date.

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Amount of liabilities classified as other, due after one year or the normal operating cycle, if longer.

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Obligations not otherwise itemized or categorized in the footnotes to the financial statements that are expected to be paid after one year (or the normal operating cycle, if longer), from the balance sheet date.

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