Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis

The following table summarizes the financial instruments measured at fair value on a recurring basis classified in the fair value hierarchy (Level 1, 2 or 3) based on the inputs used for valuation in the accompanying consolidated balance sheets:

	As of December 31, 2017						As of December 31, 2016
Fair Value Measurements:	Level 1		Level 2		Level 3		Level 1		Level 2		Level 3
Marketable securities (see Note 4: Marketable Securities)
Equity securities	$	468	$	—	$	—	$	4,033	$	—	$	—
Money market funds	44,481		—		—		—		—		—
Corporate bonds	—		9,262		—		—		57,348		—
Government securities - U.S.	—		19,050		—		—		42,814		—
Government securities - Non-U.S.	—		—		—		—		233		—
Other fixed-income securities	—		4,250		—		—		10,471		—
Other securities	—		—		—		—		81		—
Total assets	$	44,949	$	32,562	$	—	$	4,033	$	110,947	$	—
Related party payable (see Note 10: Long-Term Related Party Payable)	—		—		98,925		—		—		169,347
Total liabilities	$	—	$	—	$	98,925	$	—	$	—	$	169,347