4. Cash and cash equivalents

Cash and cash equivalents consisted of the following:

	June 30, 2013		December 31, 2012
Cash and cash equivalents:
Cash	$	6,927	$	16,677
Money market accounts	41,165		39,001
Marketable securities	—		2,460
Total cash and cash equivalents	$	48,092	$	58,138

Marketable securities consist primarily of corporate securities which include commercial paper and corporate debt instruments including notes issued by foreign or domestic corporations which pay in U.S. dollars and carry a rating of A or better with original maturities of three months or less. For the six months ended June 30, 2013 and 2012, interest income was $104 and $82, respectively, which is included in interest and other income, net in the accompanying condensed consolidated statements of operations.