Cash and Cash Equivalents, Investments and Restricted Cash - Amortized Cost, Gross Unrealized Gains and Losses, and Estimated Fair Market Value of Cash and Cash Equivalents and Available-for-Sale Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Cash and Cash Equivalents, at Carrying Value [Abstract]
Cash and cash equivalents	$ 2,611,499	$ 1,703,130
Short-term investments:
Amortized Cost	581,900
Gross Unrealized Gains		122
Gross Unrealized Losses		(59)
Estimated Fair Market Value	589,025
Restricted cash	226,651	75,805
Beneficial interest in securitizations, Amortized cost	66,167
Beneficial interest in securitizations, Gross Unrealized Gains	8,936
Beneficial interest in securitizations, Gross Unrealized Losses	0
Beneficial interests in securitizations	75,103	0
Amortized Cost, Total	3,420,050	3,996,980
Gross Unrealized Gains, Total	8,939
Gross Unrealized Losses, Total	(1,814)
Estimated Fair Market Value, Total	3,427,175	3,997,043
U.S. government agency securities
Short-term investments:
Amortized Cost	472,570	1,037,572
Gross Unrealized Gains	0	57
Gross Unrealized Losses	(1,719)	(52)
Estimated Fair Market Value	470,851	1,037,577
Corporate bonds
Short-term investments:
Amortized Cost	33,172
Gross Unrealized Gains	3
Gross Unrealized Losses	(95)
Estimated Fair Market Value	33,080
Commercial paper
Short-term investments:
Amortized Cost	9,991
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Estimated Fair Market Value	9,991
Treasury bills
Short-term investments:
Amortized Cost		1,163,748
Gross Unrealized Gains		65
Gross Unrealized Losses		0
Estimated Fair Market Value		1,163,813
Municipal securities
Short-term investments:
Amortized Cost		16,226
Gross Unrealized Gains		0
Gross Unrealized Losses		(6)
Estimated Fair Market Value		16,220
Certificates of deposit
Short-term investments:
Amortized Cost		498
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Estimated Fair Market Value		498
Cash
Cash and Cash Equivalents, at Carrying Value [Abstract]
Cash and cash equivalents	479,110	213,518
Money market funds
Cash and Cash Equivalents, at Carrying Value [Abstract]
Cash and cash equivalents	$ 2,132,389	1,486,384
Municipal securities
Cash and Cash Equivalents, at Carrying Value [Abstract]
Cash and cash equivalents		3,228
Cash and cash equivalents, at cost		3,229
Cash and cash equivalents, gross unrealized losses		$ (1)