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Primary investment in cash to repurchase common stock value.

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Purchase price as percentage of market value under employee stock purchase plan.

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Threshold limit of common stock value per employee under employee stock purchase plan.

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Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Aggregate number of common shares reserved for future issuance.

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Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

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Description of voting rights of common stock. Includes eligibility to vote and votes per share owned. Include also, if any, unusual voting rights.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Unrecognized cost of unvested options awarded to employees as compensation.

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Aggregate share number for all nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) held by stockholders. Does not include preferred shares that have been repurchased.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Number of additional shares authorized for issuance under an established share-based compensation plan.

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The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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Gross number of share options (or share units) granted during the period.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Maximum number of shares that may be issued in accordance with the plan as a proportion of outstanding capital stock.

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Price of a single share of a number of saleable stocks of a company.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Number of new stock issued during the period.

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Stockholders' Equity - Additional Information (Detail) - USD ($)					1 Months Ended	12 Months Ended
	Jan. 01, 2017	Jan. 01, 2016	Apr. 07, 2015	Jan. 11, 2015	Sep. 30, 2013	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2013	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares outstanding						36,541,770	35,281,001
Voting right of common stockholders						one vote per share
Preferred stock, shares outstanding						0
Stock-based compensation expense						$ 22,202,000	$ 19,524,000	$ 11,176,000
Number of stock options granted						0
Total shares of common stock available for issuance						5,892,594	5,750,917
Unvested Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total shares of common stock available for issuance						1,164,040	1,297,054
Common Stock Options Outstanding [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total shares of common stock available for issuance						666,717	1,267,329
2010 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock										1,162,500
Common stock available for issuance									4,232,500
2013 Stock Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock									1,355,171
Common stock available for issuance									512,568
Increase in shares available for issuance	1,461,671	1,380,949
Percentage increase in shares available for issuance						4.00%
Total shares of common stock available for issuance						3,273,334	2,398,031
2010 and 2013 Stock Incentive Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted period						4 years
Options are exercisable from date of grant for a period						10 years
2010 and 2013 Stock Incentive Plans [Member] \| Unvested Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense						$ 19,803,000	$ 16,072,000	5,615,000
2010 and 2013 Stock Incentive Plans [Member] \| Common Stock Options Outstanding [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense						2,399,000	$ 3,452,000	$ 5,561,000
Weighted-average fair value of options granted							$ 11.00	$ 26.67
Aggregate intrinsic value of stock options exercised						17,082,000	$ 2,758,000	$ 42,325,000
Unrecognized compensation cost						$ 25,635,000
Amount to be recognized over weighted-average periods						2 years 3 months 18 days
2013 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total shares of common stock available for issuance						788,503	788,503
2013 Employee Stock Purchase Plan [Member] \| Common Stock Options Outstanding [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total shares of common stock available for issuance					788,503
Description of customary employment						more than 20 hours a week
Percentage of voting power					5.00%
Percentage of eligible compensation					10.00%
Percentage of fair market value of common stock					85.00%
2013 Employee Stock Purchase Plan [Member] \| Common Stock Options Outstanding [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock value					$ 25,000
Roche [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Primary investment in cash			$ 250,000,000	$ 250,000,000
Common stock shares sold			5,000,000	5,000,000
Common stock purchase price			$ 50.00	$ 50.00
Common stock, shares outstanding			15,604,288	15,604,288