Stockholders' Equity - RSU Activities (Details) - Restricted stock units outstanding - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Number of Shares
Outstanding, beginning balance (in shares)	2,325
RSUs granted (in shares)	1,445
RSUs vested and released (in shares)	(1,204)
RSUs forfeited (in shares)	(194)
Outstanding, ending balance (in shares)	2,372	2,325
Weighted Average Grant Date Fair Value Per Share
Outstanding, beginning balance, weighted-average grant date fair value per share (in USD per share)	$ 25.36
Weighted average grant date fair value per share of RSUs granted (in USD per share)	53.33	$ 32.30	$ 18.29
RSUs vested and released, weighted-average grant date fair value per share (in USD per share)	26.29
RSUs forfeited, weighted-average grant date fair value per share (in USD per share)	32.60
Outstanding, ending balance, weighted-average grant date fair value per share (in USD per share)	41.32	25.36
Weighted average grant date fair value per share of RSUs granted (in USD per share)	$ 53.33	$ 32.30	$ 18.29
Total fair value of RSUs vested during the period	$ 68,072	$ 41,245	$ 21,161

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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