Investments (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Amortized cost	$ 45,502	$ 22,708
Available-for-sale, Gross unrealized gain	8	3
Available-for-sale, Gross unrealized losses	(12)	(1)
Available-for-sale, Estimated fair value	$ 45,498	$ 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	$ 37,010	$ 21,208
Available-for-sale, Gross unrealized gain	1	3
Available-for-sale, Gross unrealized losses	(12)	(1)
Available-for-sale, Estimated fair value	$ 36,999	$ 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	$ 8,492	$ 1,500
Available-for-sale, Gross unrealized gain	7	0
Available-for-sale, Gross unrealized losses	0	0
Available-for-sale, Estimated fair value	$ 8,499	$ 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

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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.

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-Publisher FASB

-Name Accounting Standards Codification

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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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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.

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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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