Fair Value Measurements - Assets and liabilities measured at fair value on a recurring basis (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Fair Value
Assets, Carrying Amount	$ 5,788,826	$ 2,251,282
Liabilities, Carrying amount	957,957	784,363
Recurring basis | Level 1 | Cash and cash equivalents
Fair Value
Assets, Fair Value	87,573
Recurring basis | Level 1 | U.S. Treasuries
Fair Value
Assets, Fair Value	170,477
Recurring basis | Level 1 | Equity securities
Fair Value
Assets, Fair Value	120,302
Recurring basis | Level 2 | Convertible senior notes
Fair Value
Liabilities, Fair value	1,320,194	1,272,766
Recurring basis | Level 2 | Cash and cash equivalents
Fair Value
Assets, Fair Value	53,740
Recurring basis | Level 2 | Corporate bonds
Fair Value
Assets, Fair Value	705,084
Recurring basis | Level 2 | Commercial paper
Fair Value
Assets, Fair Value	329,722
Recurring basis | Level 2 | Municipal debt
Fair Value
Assets, Fair Value	9,984
Recurring basis | Level 2 | Certificates of deposit
Fair Value
Assets, Fair Value	27,454
Recurring basis | Level 3 | Contingent consideration
Fair Value
Liabilities, Fair value	9,990	9,760
Recurring basis | Level 3 | Long-term debt
Fair Value
Liabilities, Fair value	160,484	175,402
Recurring basis | Level 3 | Finance obligations
Fair Value
Liabilities, Fair value	195,805	181,553
Carrying value | Recurring basis | Contingent consideration
Fair Value
Liabilities, Carrying amount	9,990	9,760
Carrying value | Recurring basis | Convertible senior notes
Fair Value
Liabilities, Carrying amount	192,011	85,640
Carrying value | Recurring basis | Long-term debt
Fair Value
Liabilities, Carrying amount	160,484	175,402
Carrying value | Recurring basis | Finance obligations
Fair Value
Liabilities, Carrying amount	195,805	181,553
Carrying value | Recurring basis | Cash and cash equivalents
Fair Value
Assets, Carrying Amount	141,313
Carrying value | Recurring basis | Corporate bonds
Fair Value
Assets, Carrying Amount	705,084
Carrying value | Recurring basis | Commercial paper
Fair Value
Assets, Carrying Amount	329,722
Carrying value | Recurring basis | U.S. Treasuries
Fair Value
Assets, Carrying Amount	170,477
Carrying value | Recurring basis | Municipal debt
Fair Value
Assets, Carrying Amount	9,984
Carrying value | Recurring basis | Certificates of deposit
Fair Value
Assets, Carrying Amount	27,454
Carrying value | Recurring basis | Equity securities
Fair Value
Assets, Carrying Amount	120,302
Fair value | Recurring basis | Contingent consideration
Fair Value
Liabilities, Fair value	9,990	9,760
Fair value | Recurring basis | Convertible senior notes
Fair Value
Liabilities, Fair value	1,320,194	1,272,766
Fair value | Recurring basis | Long-term debt
Fair Value
Liabilities, Fair value	160,484	175,402
Fair value | Recurring basis | Finance obligations
Fair Value
Liabilities, Fair value	195,805	$ 181,553
Fair value | Recurring basis | Cash and cash equivalents
Fair Value
Assets, Fair Value	141,313
Fair value | Recurring basis | Corporate bonds
Fair Value
Assets, Fair Value	705,084
Fair value | Recurring basis | Commercial paper
Fair Value
Assets, Fair Value	329,722
Fair value | Recurring basis | U.S. Treasuries
Fair Value
Assets, Fair Value	170,477
Fair value | Recurring basis | Municipal debt
Fair Value
Assets, Fair Value	9,984
Fair value | Recurring basis | Certificates of deposit
Fair Value
Assets, Fair Value	27,454
Fair value | Recurring basis | Equity securities
Fair Value
Assets, Fair Value	$ 120,302