Other Balance Sheet Amounts (Investments in Marketable Securities) (Details) - Available-for-sale — short-term: - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 38,609	$ 40,551
Gross Unrealized Gains	0	1
Gross Unrealized Losses	(5)	(2)
Fair Value	38,604	40,550
U.S. Treasury, government and agency debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	18,255	23,237
Gross Unrealized Gains	0	1
Gross Unrealized Losses	(5)	(2)
Fair Value	18,250	23,236
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	20,354	17,314
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	$ 20,354	$ 17,314