Marketable Securities - Fair Value of Available for Sale Marketable Securities (Detail) - Level 2 [Member] - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Adjusted Cost	$ 85,486	$ 39,010
Available for sale securities, Unrealized Gains	0	0
Available for sale securities, Unrealized Losses	(78)	(37)
Available for sale securities, Fair Value	85,408	38,973
Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Adjusted Cost	6,291	6,278
Available for sale securities, Unrealized Gains	0	0
Available for sale securities, Fair Value	6,291	6,278
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Adjusted Cost	79,195	32,732
Available for sale securities, Unrealized Gains	0	0
Available for sale securities, Unrealized Losses	(78)	(37)
Available for sale securities, Fair Value	$ 79,117	$ 32,695

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

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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

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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

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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

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