Fair Value Measurements (Details) - USD ($) $ in Thousands		Jun. 30, 2022		Dec. 31, 2021		Jun. 30, 2021
Fair Value Measurements [Abstract]
Available-for-sale securities		$ 1,523,267		$ 1,248,124
Equity securities		$ 45,110		$ 50,527
0.125% Notes [Member]
Fair Value Measurements [Abstract]
Interest rate on convertible senior notes		0.125%		0.125%		0.125%
0% Notes [Member]
Fair Value Measurements [Abstract]
Interest rate on convertible senior notes		0.00%		0.00%		0.00%
Publicly Traded Equity Securities [Member]
Fair Value Measurements [Abstract]
Equity securities		$ 4,738		$ 18,205
Privately Held Equity Securities [Member]
Fair Value Measurements [Abstract]
Equity securities		40,372		32,322
Significant Other Observable Inputs (Level 2) [Member] | 0.125% Notes [Member]
Fair Value Measurements [Abstract]
Fair value of convertible notes		485,200
Significant Other Observable Inputs (Level 2) [Member] | 0% Notes [Member]
Fair Value Measurements [Abstract]
Fair value of convertible notes		577,000
Recurring Basis [Member]
Fair Value Measurements [Abstract]
Cash equivalents	[1]	409,877		541,199
Total		1,978,254		1,839,850
Recurring Basis [Member] | Corporate Debt Securities [Member]
Fair Value Measurements [Abstract]
Available-for-sale securities	[2]	760,856		764,059
Recurring Basis [Member] | Debt Securities Issued by U.S. Government Agencies [Member]
Fair Value Measurements [Abstract]
Available-for-sale securities	[2]	88,374		120,868
Recurring Basis [Member] | Debt Securities Issued by the U.S. Treasury [Member]
Fair Value Measurements [Abstract]
Available-for-sale securities	[2]	494,122		182,634
Recurring Basis [Member] | Debt Securities Issued by States of the U.S. and Political Subdivisions of the States [Member]
Fair Value Measurements [Abstract]
Available-for-sale securities		173,621	[3]	174,464	[4]
Recurring Basis [Member] | Debt Securities Issued by States of the U.S. and Political Subdivisions of the States [Member] | Cash and Cash Equivalents [Member]
Fair Value Measurements [Abstract]
Available-for-sale securities		23,400		2,300
Recurring Basis [Member] | Other Municipal Debt Securities [Member]
Fair Value Measurements [Abstract]
Available-for-sale securities	[2]	6,294		6,099
Recurring Basis [Member] | Publicly Traded Equity Securities [Member]
Fair Value Measurements [Abstract]
Equity securities		4,738		18,205
Recurring Basis [Member] | Privately Held Equity Securities [Member]
Fair Value Measurements [Abstract]
Equity securities		40,372		32,322
Recurring Basis [Member] | Quoted Prices in Active Markets (Level 1) [Member]
Fair Value Measurements [Abstract]
Cash equivalents		409,877		541,199
Total		904,375		727,708
Recurring Basis [Member] | Quoted Prices in Active Markets (Level 1) [Member] | Corporate Debt Securities [Member]
Fair Value Measurements [Abstract]
Available-for-sale securities		0		0
Recurring Basis [Member] | Quoted Prices in Active Markets (Level 1) [Member] | Debt Securities Issued by U.S. Government Agencies [Member]
Fair Value Measurements [Abstract]
Available-for-sale securities		0		0
Recurring Basis [Member] | Quoted Prices in Active Markets (Level 1) [Member] | Debt Securities Issued by the U.S. Treasury [Member]
Fair Value Measurements [Abstract]
Available-for-sale securities		494,122		182,634
Recurring Basis [Member] | Quoted Prices in Active Markets (Level 1) [Member] | Debt Securities Issued by States of the U.S. and Political Subdivisions of the States [Member]
Fair Value Measurements [Abstract]
Available-for-sale securities		0		0
Recurring Basis [Member] | Quoted Prices in Active Markets (Level 1) [Member] | Other Municipal Debt Securities [Member]
Fair Value Measurements [Abstract]
Available-for-sale securities		0		0
Recurring Basis [Member] | Quoted Prices in Active Markets (Level 1) [Member] | Publicly Traded Equity Securities [Member]
Fair Value Measurements [Abstract]
Equity securities		376		3,875
Recurring Basis [Member] | Quoted Prices in Active Markets (Level 1) [Member] | Privately Held Equity Securities [Member]
Fair Value Measurements [Abstract]
Equity securities		0		0
Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value Measurements [Abstract]
Cash equivalents		0		0
Total		1,029,145		1,065,490
Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Corporate Debt Securities [Member]
Fair Value Measurements [Abstract]
Available-for-sale securities		760,856		764,059
Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Debt Securities Issued by U.S. Government Agencies [Member]
Fair Value Measurements [Abstract]
Available-for-sale securities		88,374		120,868
Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Debt Securities Issued by the U.S. Treasury [Member]
Fair Value Measurements [Abstract]
Available-for-sale securities		0		0
Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Debt Securities Issued by States of the U.S. and Political Subdivisions of the States [Member]
Fair Value Measurements [Abstract]
Available-for-sale securities		173,621		174,464
Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Municipal Debt Securities [Member]
Fair Value Measurements [Abstract]
Available-for-sale securities		6,294		6,099
Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Publicly Traded Equity Securities [Member]
Fair Value Measurements [Abstract]
Equity securities		0		0
Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Privately Held Equity Securities [Member]
Fair Value Measurements [Abstract]
Equity securities		0		0
Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Measurements [Abstract]
Cash equivalents		0		0
Total		44,734		46,652
Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member] | Corporate Debt Securities [Member]
Fair Value Measurements [Abstract]
Available-for-sale securities		0		0
Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member] | Debt Securities Issued by U.S. Government Agencies [Member]
Fair Value Measurements [Abstract]
Available-for-sale securities		0		0
Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member] | Debt Securities Issued by the U.S. Treasury [Member]
Fair Value Measurements [Abstract]
Available-for-sale securities		0		0
Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member] | Debt Securities Issued by States of the U.S. and Political Subdivisions of the States [Member]
Fair Value Measurements [Abstract]
Available-for-sale securities		0		0
Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Municipal Debt Securities [Member]
Fair Value Measurements [Abstract]
Available-for-sale securities		0		0
Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member] | Publicly Traded Equity Securities [Member]
Fair Value Measurements [Abstract]
Equity securities		4,362		14,330
Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member] | Privately Held Equity Securities [Member]
Fair Value Measurements [Abstract]
Equity securities		$ 40,372		$ 32,322

[1] Included in cash and cash equivalents on our condensed consolidated balance sheet.

[2] Included in short-term investments.

[3] $23.4 million was included in cash and cash equivalents on our condensed consolidated balance sheet, with the difference included in short-term investments on our condensed consolidated balance sheet.

[4] $2.3 million was included in cash and cash equivalents on our condensed consolidated balance sheet, with the difference included in short-term investments on our condensed consolidated balance sheet.