Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2013

Fair Value Disclosures [Abstract]

Financial Assets Measured at Fair Value on a Recurring Basis

The following table presents information about our financial assets that have been measured at fair value on a recurring basis as of June 30, 2013 and December 31, 2012, and indicates the fair value hierarchy of the valuation inputs utilized to determine such fair value (in thousands).

	Fair Value Measurements as of
	June 30, 2013
	Total		Level 1		Level 2		Level 3
Cash equivalents:
Money market funds	$	12,788	$	2	$	12,786	$	—
Corporate notes and bonds	63,490		—		63,490		—
Short-term investments:
Corporate notes and bonds	73,135		—		73,135		—
U.S. government agency securities	34,401		34,276		125		—
Restricted cash equivalents and investments	10,000		—		10,000		—
Equity investments in publicly traded securities	36,156		36,156		—		—
Total	$	229,970	$	70,434	$	159,536	$	—

	Fair Value Measurements as of
	December 31, 2012
	Total		Level 1		Level 2		Level 3
Cash equivalents:
Money market funds	$	10,680	$	—	$	10,680	$	—
Corporate notes and bonds	81,235		—		81,235		—
Short-term investments:
Corporate notes and bonds	65,502		—		65,502		—
U.S. government agency securities	42,714		42,113		601		—
Restricted cash equivalents and investments	10,000		—		10,000		—
Equity investments in publicly traded securities	34,334		34,334		—		—
Total	$	244,465	$	76,447	$	168,018	$	—