Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 203,298	$ 142,882
Gross unrealized gains	94	44
Gross unrealized losses	(35)	(49)
Fair value	203,357	142,877
Government-sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	29,109	22,055
Gross unrealized gains	12	1
Gross unrealized losses	0	(9)
Fair value	29,121	22,047
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	168,927	111,473
Gross unrealized gains	81	42
Gross unrealized losses	(35)	(34)
Fair value	168,973	111,481
U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	5,262	9,354
Gross unrealized gains	1	1
Gross unrealized losses	0	(6)
Fair value	$ 5,263	$ 9,349

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

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
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-Publisher FASB
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Amount of debt securities categorized neither as held-to-maturity nor trading.

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