Financial Instruments - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss	$ 0	$ 0
Equity Securities without Readily Determinable Fair Value, Amount	2,000
Debt Securities, Available-for-sale, Unrealized Loss Position	0	46,550
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	0	22
Interest Receivable	$ 108	$ 183
Share Price	$ 68.63
1.75% Convertible Senior Notes due 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Aggregate Principal Amount	$ 25,626
Convertible Senior Notes due 2025
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Aggregate Principal Amount	$ 661,250

Face (par) amount of debt instrument at time of issuance.

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