4.	Balance Sheet Components

Cash and Cash Equivalents

Cash and cash equivalents consisted of the following (in thousands):

	March 31, 2018		December 31, 2017
Cash	$	69,559	$	103,716
Money market funds		589,448		569,942
Total cash and cash equivalents	$	659,007	$	673,658

At March 31, 2018 and December 31, 2017, a total of $27.7 million and $32.3 million, respectively, of the Company’s cash and cash equivalents were held outside of the U.S. in its foreign subsidiaries to be used primarily for its China operations.

Investments

The Company’s investments consist of available-for-sale debt investments and marketable equity investments. The amortized cost, gross unrealized holding gains or losses, and fair value of the Company’s available-for-sale investments by major investments type are summarized in the tables below (in thousands):

	March 31, 2018
	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Fair Value
Corporate bonds	$	36,529	$	—	$	(92	)	$	36,437
Bond and mutual funds		17,293		1,338		—			18,631
Equity investments		125		74		—			199
Total investments	$	53,947	$	1,412	$	(92	)	$	55,267

	December 31, 2017
	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Fair Value
Corporate bonds	$	53,985	$	4	$	(46	)	$	53,943
Bond and mutual funds		17,249		1,153		—			18,402
Equity investments		126		95		—			221
Total investments	$	71,360	$	1,252	$	(46	)	$	72,566

At March 31, 2018, all of the available-for-sale investments had contractual maturities within one year. The Company periodically reviews its available-for-sale investments for other-than-temporary impairment. The Company considers factors such as the duration, severity and the reason for the decline in value, the potential recovery period and its intent to sell. For debt securities, the Company also considers whether (i) it is more likely than not that the Company will be required to sell the debt securities before recovery of their amortized cost basis, and (ii) the amortized cost basis cannot be recovered as a result of credit losses. During the three months ended March 31, 2018, the Company did not recognize any other-than-temporary impairment loss.

Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):

	March 31, 2018		December 31, 2017
Preclinical and clinical trial accruals	$	37,717	$	32,321
Payroll and related accruals		11,919		18,810
Property taxes and other		3,150		4,201
Professional services		2,520		1,991
Other		7,553		6,458
Total accrued liabilities	$	62,859	$	63,781