5.	Balance Sheet Components

Cash and Cash Equivalents

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

	December 31,
	2017		2016
Cash	$	103,716	$	79,239
Money market funds		569,942		94,543
Total cash and cash equivalents	$	673,658	$	173,782

Property and Equipment

Property and equipment consisted of the following (in thousands):

	December 31,
	2017			2016
Laboratory equipment	$	19,497		$	18,533
Computer equipment		6,006			5,678
Furniture and fixtures		5,575			5,533
Leasehold improvements		93,758			93,564
Building shell (Refer to Note 8)		53,879			53,879
Construction in progress		10,402			109
Total property and equipment	$	189,117		$	177,296
Less: accumulated depreciation		(59,641	)		(53,639	)
Property and equipment, net	$	129,476		$	123,657

Depreciation expense for the years ended December 31, 2017, 2016 and 2015 was $6.1 million, $6.0 million, and $5.7 million, respectively.

Investments

All investments are classified as available-for-sale. 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):

	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

	December 31, 2016
	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Fair Value
Corporate bonds	$	126,550	$	182	$	(49	)	$	126,683
Certificate of deposits		1,037		—		—			1,037
Bond and mutual funds		22,305		157		—			22,462
Equity investments		125		100		—			225
Total investments	$	150,017	$	439	$	(49	)	$	150,407

The contractual maturities of available-for-sale investments were as follows (in thousands):

	December 31, 2017
Within one year	$	53,943
After one year through four years		—
Total debt investments		53,943
Bond and mutual funds		18,402
Equity investments		221
Total investments	$	72,566

Available-for-sale investments are reported at fair value and as such, their associated unrealized gains and losses are reported as a separate component of stockholders’ equity within accumulated other comprehensive income (loss).

Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):

	December 31,
	2017		2016
Preclinical and clinical trial accruals	$	32,321	$	29,550
Payroll and related accruals		18,810		14,232
Property taxes and other		4,201		451
Professional services		1,991		1,252
Other		6,458		5,429
Total accrued liabilities	$	63,781	$	50,914