Fair Value Measurements (Tables)
9 Months Ended
Sep. 30, 2016
Fair Value Disclosures [Abstract]  
Fair value of financial assets and liabilities
As of September 30, 2016 and December 31, 2015, the fair value of our financial assets was as follows:
 
Level 1
 
Level 2
 
Level 3
 
Total
 
(in thousands)
September 30, 2016
 
 
 
 
 
 
 
Assets:
 
 
 
 
 
 
 
Money market funds (1)
$
14,733

 
$
—

 
$
—

 
$
14,733

Corporate bonds (2)
—

 
100,852

 
—

 
100,852

Government securities (2)
—

 
9,705

 
—

 
9,705

Commercial paper (2)
—

 
8,187

 
—

 
8,187

Agency securities (2)
—

 
7,258

 
—

 
7,258

Municipal bonds (2)
—

 
4,048

 
—

 
4,048

Certificates of deposit (2)
—

 
1,248

 
—

 
1,248

Total assets measured at fair value
$
14,733

 
$
131,298

 
$
—

 
$
146,031

December 31, 2015
 
 
 
 
 
 
 
Assets:
 
 
 
 
 
 
 
Money market funds (1)
$
18,114

 
$
—

 
$
—

 
$
18,114

Corporate bonds (2)
—

 
124,829

 
—

 
124,829

Commercial paper (3)
—

 
47,294

 
—

 
47,294

Municipal bonds (2)
—

 
16,223

 
—

 
16,223

Government securities (2)
—

 
8,688

 
—

 
8,688

Agency securities (2)
—

 
7,253

 
—

 
7,253

Certificates of deposit (2)
—

 
2,244

 
—

 
2,244

Total assets measured at fair value
$
18,114

 
$
206,531

 
$
—

 
$
224,645


(1) 
Classified in cash and cash equivalents
(2) 
Classified in marketable securities.
(3) 
Includes commercial paper with maturities of three months or less at time of purchase of $10.1 million classified in cash and cash equivalents and commercial paper with maturities of greater than three months of $37.2 million classified in marketable securities.