Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Available-for-sale Securities
One year or less	$ 22,918	$ 64,866
One year through three years	29,005	29,928
Estimated Fair Value	51,923	94,794
Short-term
Available-for-sale Securities
Amortized Cost	22,932	64,922
Gross Unrealized Gains	2	3
Gross Unrealized Losses	(16)	(59)
Estimated Fair Value	22,918	64,866
Short-term \| Agency securities
Available-for-sale Securities
Amortized Cost	6,246	0
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(2)	0
Estimated Fair Value	6,244	0
Short-term \| Commercial paper
Available-for-sale Securities
Amortized Cost	499
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Estimated Fair Value	499
Short-term \| Corporate debt securities
Available-for-sale Securities
Amortized Cost	16,187	64,922
Gross Unrealized Gains	2	3
Gross Unrealized Losses	(14)	(59)
Estimated Fair Value	16,175	64,866
Long-term
Available-for-sale Securities
Amortized Cost	29,102	29,959
Gross Unrealized Gains	1	6
Gross Unrealized Losses	(98)	(37)
Estimated Fair Value	29,005	29,928
Long-term \| Agency securities
Available-for-sale Securities
Amortized Cost	13,421	13,649
Gross Unrealized Gains	1	3
Gross Unrealized Losses	(43)	(7)
Estimated Fair Value	13,379	13,645
Long-term \| US Government securities
Available-for-sale Securities
Amortized Cost	5,549	1,799
Gross Unrealized Gains	0	2
Gross Unrealized Losses	(18)	0
Estimated Fair Value	5,531	1,801
Long-term \| Corporate debt securities
Available-for-sale Securities
Amortized Cost	10,132	14,511
Gross Unrealized Gains	0	1
Gross Unrealized Losses	(37)	(30)
Estimated Fair Value	$ 10,095	$ 14,482

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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-Publisher FASB
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