Net Income Per Share - Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Aug. 07, 2017
Numerator:
Net income, basic	$ 23,767	$ 15,033	$ 75,758	$ 34,065
Add: interest expense on 2023 Notes	1,410	1,429	4,231	0
Net income, diluted	$ 25,177	$ 16,462	$ 79,989	$ 34,065
Denominator:
Weighted-average shares used to compute basic net income per share	106,841,000	109,282,000	107,236,000	111,128,000
Dilutive effect of 2023 Notes	12,189,000	12,398,000	12,189,000	0
Dilutive effect of options and awards granted under equity incentive plan and employee stock purchase plan	766,000	313,000	695,000	455,000
Weighted-average shares used to compute diluted net income per share	119,796,000	121,993,000	120,120,000	111,583,000
Net income per share
Basic (in dollars per share)	$ 0.22	$ 0.14	$ 0.71	$ 0.31
Diluted (in dollars per share)	$ 0.21	$ 0.13	$ 0.67	$ 0.31
Convertible senior notes \| 2025 Notes
Dilutive effect of 2025 Notes	0		0
Convertible senior notes \| 2025 Notes \| Common stock
Conversion price (in dollars per share)	$ 17.26		$ 17.26		$ 17.26

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of convertible debt securities using the treasury stock method.

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The price per share of the conversion feature embedded in the debt instrument.

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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Net income after adjustments for dividends on preferred stock (declared in the period) and/or cumulative preferred stock (accumulated for the period).

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Net Income or Loss Available to Common Stockholders plus adjustments resulting from the assumption that dilutive convertible securities were converted, options or warrants were exercised, or that other shares were issued upon the satisfaction of certain conditions.

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The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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