Investments (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Amortized cost	$ 28,130	$ 22,708
Available-for-sale, Gross unrealized gain	2	3
Available-for-sale, Gross unrealized losses	0	(1)
Available-for-sale, Estimated fair value	$ 28,132	$ 22,710
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, maximum maturity period	1 year	1 year
Available-for-sale, Amortized cost	$ 25,381	$ 21,208
Available-for-sale, Gross unrealized gain	1	3
Available-for-sale, Gross unrealized losses	0	(1)
Available-for-sale, Estimated fair value	$ 25,382	$ 21,210
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, maximum maturity period	1 year	1 year
Available-for-sale, Amortized cost	$ 2,749	$ 1,500
Available-for-sale, Gross unrealized gain	1	0
Available-for-sale, Gross unrealized losses	0	0
Available-for-sale, Estimated fair value	$ 2,750	$ 1,500

Available-for-sale Securities, Maximum Maturity Period

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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-Publisher FASB

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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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