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Fair Value Measurements (Details) $ in Thousands	3 Months Ended		12 Months Ended
Fair Value Measurements (Details) $ in Thousands	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Goodwill, Impairment Loss			$ 61,661	$ 4,879
Impairment and other losses	$ 77,240	$ 6,655	96,399	8,599	$ 87,204
Operating lease charge			22,667
Impairment of right-of-use asset			9,969	3,700
Variable lease cost			14,640	18,879
Lessee, Lease Property in New York [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Variable lease cost			$ 12,698
Measurement Input, Discount Rate [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Business Combination, Contingent Consideration, Liability, Measurement Input	0.051		0.051
Senior Notes \| Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Fair Value Disclosure	$ 870,256	900,000	$ 870,256	900,000
Senior Notes \| Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Fair Value Disclosure	$ 883,580	$ 812,250	$ 883,580	$ 812,250