Cash Equivalents and Marketable Securities

At September 30, 2013, cash equivalents and marketable securities consisted of the following (in thousands):



	September 30, 2013
	Adjusted Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value		Average Contractual Maturities
									(in days)
Money market funds	$	21,079	$	—	$	—	$	21,079	n/a
Corporate bonds (unamortized cost)	1,004		3		—		1,007		151
U.S. Treasury obligations (unamortized cost)	2,000		2		—		2,002		232
Common shares of CO2 Solutions	563		$	504	$	—	1,067		n/a
Total	$	24,646	$	509	$	—	$	25,155

The total cash and cash equivalents balance of $26.9 million as of September 30, 2013 was comprised of money market funds of $21.1 million, and $5.8 million held as cash, primarily with major financial institutions in North America. At September 30, 2013, we had no marketable securities in an unrealized loss position.

At December 31, 2012, cash equivalents and marketable securities consisted of the following (in thousands):



	December 31, 2012
	Adjusted Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value		Average Contractual Maturities
									(in days)
Money market funds	$	24,789	$	—	$	—	$	24,789	n/a
Commercial paper	1,499		1		—		1,500		70
Corporate bonds (unamortized cost)	9,512		10		—		9,522		156
U.S. Treasury obligations (unamortized cost)	5,510		5		—		5,515		262
Common shares of CO2 Solutions	563		47		—		610		n/a
Total	$	41,873	$	63	$	—	$	41,936

The total cash and cash equivalents balance of $32.0 million as of December 31, 2012, was comprised of money market funds of $24.8 million and $7.2 million held as cash, primarily with major financial institutions in North America. At December 31, 2012, we had no marketable securities in an unrealized loss position.