Summary of Company Cash, Cash Equivalents and Investments (Detail) - USD ($)	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents, Amortized cost	$ 2,115,869,000	$ 1,938,549,000
Cash and cash equivalents, Gross unrealized gains		9,000
Cash and cash equivalents	2,115,869,000	1,502,648,000	$ 835,080,000
Cash, cash equivalents and investments, Amortized cost	2,115,869,000	1,502,639,000
Cash, cash equivalents and investments, Gross unrealized gains		22,000
Cash, cash equivalents and investments, Fair market value	2,115,869,000	1,938,571,000
Available for sale debt securities current, Amortized cost		435,910,000
Available for sale debt securities current, Gross unrealized gains		13,000
Available for sale debt securities current, Fair market value	0	435,923,000
Cash and Money Market Funds [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents, Amortized cost	2,115,869,000	900,590,000	$ 1,938,549,000
Cash and cash equivalents	2,115,869,000	900,590,000
Cash, cash equivalents and investments, Fair market value		1,938,571,000
Government and Government Agency Bonds [Member]
Cash and Cash Equivalents [Line Items]
Available for sale debt securities, Amortized cost		1,037,959,000
Available for sale debt securities, Gross unrealized gains		22,000
Available for sale debt securities, Fair market value		$ 1,037,981,000
Cash, cash equivalents and investments, Fair market value	$ 2,115,869,000