Marketable Securities - Summary of Marketable Securities Designated as Available-for-Sale (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 156,951	$ 196,817
Gross Unrealized Gains	26	4
Gross Unrealized Losses	(99)	(347)
Estimated Fair Value	156,878	196,474
Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	115,144	125,132
Gross Unrealized Gains	14	1
Gross Unrealized Losses	(90)	(304)
Estimated Fair Value	115,068	124,829
Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	13,130	16,228
Gross Unrealized Gains	0	2
Gross Unrealized Losses	(6)	(6)
Estimated Fair Value	13,124	16,224
Government securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	11,693	8,704
Gross Unrealized Gains	12	1
Gross Unrealized Losses	(2)	(17)
Estimated Fair Value	11,703	8,688
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	7,473	37,236
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	7,473	37,236
Agency securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	7,267	7,273
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	(20)
Estimated Fair Value	7,266	7,253
Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,244	2,244
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	$ 2,244	$ 2,244

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=65884222&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
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-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
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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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-Section 50
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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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-Paragraph 2
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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
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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