Share-Based Compensation and Benefit Plans (Stock Options) (Narrative) (Details) - Stock option [Member] - USD ($) $ / shares in Units, $ in Millions	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018
Share-Based Compensation and Benefit Plans
Weighted-average grant-date fair value of options awarded	$ 107.00	$ 74.18
Remaining unrecognized compensation expense	$ 38.7
Weighted-average period for cost recognition	2 years 9 months 18 days
Employee stock option [Member]
Share-Based Compensation and Benefit Plans
Options expiration period	10 years
Vesting period	4 years
Option vesting rate per year	25.00%
Director [Member]
Share-Based Compensation and Benefit Plans
Options expiration period	7 years
Vesting period	6 months

Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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Percentage of vesting of award under share-based payment arrangement.

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-Publisher FASB
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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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