Cash, Cash Equivalents and Investments - Effective Maturity Dates of Available-for-Sale Investments (Detail) $ in Thousands	Dec. 31, 2020 USD ($)
Debt Securities, Available-for-sale [Line Items]
Less than 1 Year	$ 103,240
1-2 Years	192,494
2-3 Years	186,604
3-4 Years	14,949
4-5 Years	1,078
Fair Value, Total	498,365
Treasury Bills [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 1 Year	35,403
1-2 Years	68,217
2-3 Years	28,241
3-4 Years	0
4-5 Years	0
Fair Value, Total	131,861
Corporate Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 1 Year	32,714
1-2 Years	69,534
2-3 Years	119,328
3-4 Years	13,488
4-5 Years	1,078
Fair Value, Total	236,142
Asset-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 1 Year	25,160
1-2 Years	46,842
2-3 Years	18,755
3-4 Years	1,461
4-5 Years	0
Fair Value, Total	92,218
Sovereign Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 1 Year	8,660
1-2 Years	0
2-3 Years	3,440
3-4 Years	0
4-5 Years	0
Fair Value, Total	12,100
Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 1 Year	1,303
1-2 Years	5,096
2-3 Years	639
3-4 Years	0
4-5 Years	0
Fair Value, Total	7,038
Agency Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 1 Year	0
1-2 Years	2,805
2-3 Years	16,201
3-4 Years	0
4-5 Years	0
Fair Value, Total	$ 19,006