FAIR VALUE MEASUREMENTS (Tables)

6 Months Ended

Jun. 30, 2016

FAIR VALUE MEASUREMENTS

Summary of the levels of the fair value hierarchy into which the Company's financial assets and liabilities fall

        The following table summarizes the levels of the fair value hierarchy into which the Company's financial assets and liabilities fall as of June 30, 2016:

Financial assets:	Total		Level 1		Level 2		Level 3
Included in cash and cash equivalents
U.S. treasury bills	$	19,997	$	9,997		10,000		—
Government securities money market		53,351		—		53,351		—
Investments
U.S. treasury bills		62,969		7,984		54,985		—
Convertible notes		678		—		—		678
Total financial assets	$	136,995	$	17,981	$	118,336	$	678

        The following table summarizes the levels of the fair value hierarchy into which the Company's financial assets fall as of December 31, 2015:

Financial assets:	Total		Level 1		Level 2		Level 3
Included in cash and cash equivalents
U.S. treasury bills	$	100,996	$	71,998	$	28,998	$	—
Government securities money market		77,876		—		77,876		—
Investments
U.S. treasury bills		37,989		19,990		17,999		—
Convertible notes		635		—		—		635
Total financial assets	$	217,496	$	91,988	$	124,873	$	635

Schedule of changes to the Company's investment classified as Level 3

	Convertible notes
January 1, 2016	$	635
Unrealized gains (losses) included in accumulated other comprehensive income		43
June 30, 2016	$	678
Unrealized gains (losses) related to investment still held as of June 30, 2016	$	43