Stockholders' Equity - Stock Option Plan and Restricted Stock Activity (Details)	9 Months Ended
Sep. 30, 2019 $ / shares shares
Stock Options
Stock Options
Balance at beginning of period (shares) \| shares	1,736,304
Granted (shares) \| shares	319,334
Options exercised (shares) \| shares	(111,010)
Forfeited (shares) \| shares	(5,000)
Balance at end of period (shares) \| shares	1,939,628
Weighted- Average Exercise Price
Balance at beginning of period (USD per share) \| $ / shares	$ 66.71
Granted (USD per share) \| $ / shares	117.07
Options exercised (USD per share) \| $ / shares	23.67
Forfeited (USD per share) \| $ / shares	136.72
Balance at end of period (USD per share) \| $ / shares	$ 77.24
Restricted Stock Awards
Restricted Stock Awards
Nonvested at beginning of period (shares) \| shares	132,273
Granted (shares) \| shares	101,404
RSUs vested (shares) \| shares	(70,166)
Forfeited (shares) \| shares	(666)
Nonvested at end of period (shares) \| shares	162,845
Weighted- Average Grant Date Fair Value
Nonvested at beginning of period (USD per share) \| $ / shares	$ 130.63
Granted (USD per share) \| $ / shares	113.48
RSUs vested (USD per share) \| $ / shares	110.99
Forfeited (USD per share) \| $ / shares	134.36
Nonvested at end of period (USD per share) \| $ / shares	$ 128.40

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

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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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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.

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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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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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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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

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Number of options outstanding, including both vested and non-vested options.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Number of share options (or share units) exercised during the current period.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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