FAIR VALUE MEASUREMENTS (Tables)

3 Months Ended

Mar. 31, 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 tables summarize the levels of the fair value hierarchy into which the Company's financial assets and liabilities fall as of March 31, 2016:

	Total		Level 1		Level 2		Level 3
Financial assets:
Included in cash and cash equivalents
U.S. treasury bills	$	29,991	$	29,991		—		—
Government securities money market		30,346		—		30,346		—
Investments
U.S. treasury bills		47,972		19,974		27,998		—
Convertible notes		657		—		—		657
Total financial assets	$	108,966	$	49,965	$	58,344	$	657

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

	Total		Level 1		Level 2		Level 3
Financial assets:
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		22
March 31, 2016	$	657
Unrealized gains (losses) related to investment still held as of March 31, 2016	$	22