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Fair Value Measurement - Narrative (Details) - USD ($)	6 Months Ended
Fair Value Measurement - Narrative (Details) - USD ($)	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Oct. 20, 2020	Aug. 13, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment charges	$ 0	$ 0
2027 Notes \| Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate					4.625%
2029 Notes \| Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate				4.00%
Fair Value, Measurements, Nonrecurring \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investment balance	17,220,000		$ 15,449,000
Commercial paper \| Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial paper	55,353,000		58,345,000
Commercial paper \| Fair Value, Measurements, Recurring \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial paper	55,353,000		58,345,000
Available-for-sale securities	$ 12,507,000		$ 25,196,000