Stockholders' Equity - RSU, RSA Activity Under Equity-Based Plans (Details)	9 Months Ended
Sep. 30, 2019 $ / shares shares
RSUs
Number of Units
Nonvested At Dec 31, 2018 (in shares) \| shares	1,737,554
Granted (in shares) \| shares	678,936
Vested (in shares) \| shares	(710,291)
Forfeited (in shares) \| shares	(147,622)
Nonvested At September 30, 2019 (in shares) \| shares	1,558,577
Weighted-Average Grant Date Fair Value
Nonvested at Dec 31, 2018 (in dollars per share) \| $ / shares	$ 32.83
Granted (in dollars per share) \| $ / shares	60.79
Vested (in dollars per share) \| $ / shares	31.12
Forfeited (in dollars per share) \| $ / shares	37.55
Nonvested at September 30, 2019 (in dollars per share) \| $ / shares	$ 44.63
RSAs
Number of Units
Nonvested At Dec 31, 2018 (in shares) \| shares	346,792
Granted (in shares) \| shares	0
Vested (in shares) \| shares	(38,042)
Forfeited (in shares) \| shares	(11,103)
Nonvested At September 30, 2019 (in shares) \| shares	297,647
Weighted-Average Grant Date Fair Value
Nonvested at Dec 31, 2018 (in dollars per share) \| $ / shares	$ 49.13
Granted (in dollars per share) \| $ / shares	0
Vested (in dollars per share) \| $ / shares	50.37
Forfeited (in dollars per share) \| $ / shares	49.35
Nonvested at September 30, 2019 (in dollars per share) \| $ / shares	$ 49.11

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(3)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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- Definition

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.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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- Definition

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).

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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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).

+ References

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-Publisher FASB
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- Definition

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.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
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-Paragraph 2
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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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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.

+ References

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