Balance Sheet Account Details - Investment Categories (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Short-term investments
Debt Securities, Available-for-sale [Line Items]
Cost	$ 941,174	$ 600,154
Gross unrealized gains	933	1,226
Gross unrealized losses	(2,118)	(163)
Estimated fair value	939,989	601,217
Bank deposits
Debt Securities, Available-for-sale [Line Items]
Cost	411,690	311,066
Gross unrealized gains	188	26
Gross unrealized losses	(3)	(29)
Estimated fair value	411,875	311,063
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Cost	63,818	53,223
Gross unrealized gains	161	1
Gross unrealized losses	0	(45)
Estimated fair value	63,979	53,179
Corporate equity securities
Debt Securities, Available-for-sale [Line Items]
Cost	4,506	135
Gross unrealized gains	416	1,191
Gross unrealized losses	(1,850)	0
Estimated fair value	3,072	1,326
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Cost	210,525	225,731
Gross unrealized gains	43	8
Gross unrealized losses	(16)	(76)
Estimated fair value	210,552	225,663
Warrants
Debt Securities, Available-for-sale [Line Items]
Cost	0
Gross unrealized gains	125
Gross unrealized losses	0
Estimated fair value	125
Mutual fund
Debt Securities, Available-for-sale [Line Items]
Cost	250,635
Gross unrealized gains	0
Gross unrealized losses	(249)
Estimated fair value	$ 250,386
U.S. Government bonds
Debt Securities, Available-for-sale [Line Items]
Cost		7,982
Gross unrealized gains		0
Gross unrealized losses		(9)
Estimated fair value		7,973
Municipal bonds
Debt Securities, Available-for-sale [Line Items]
Cost		2,017
Gross unrealized gains		0
Gross unrealized losses		(4)
Estimated fair value		$ 2,013