Marketable Securities and Fair Value Measurements - Summary of Available-for-Sale Marketable Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 50,447	$ 50,575
Gross Unrealized Gains	75	28
Gross Unrealized Losses		(15)
Estimated Fair Value	50,522	50,588
U.S. Treasuries
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	49,947	50,075
Gross Unrealized Gains	68	22
Gross Unrealized Losses		(15)
Estimated Fair Value	50,015	50,082
Mutual Funds
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	500	500
Gross Unrealized Gains	7	6
Estimated Fair Value	$ 507	$ 506

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

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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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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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