Share Based Award Stock Options Granted and Valuation (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Time-based stock option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options granted	5,815	8,825	13,405
Time based options grant date fair value	$ 425	$ 375	$ 413
Expected term (years)	5 years 6 months	5 years 6 months	5 years 6 months
Expected stock price volatility	24.00%	27.00%	31.80%
Risk-Free Interest Rate	2.30%	1.10%	0.70%
Expected Dividend Yield	0.00%	0.00%	0.00%
Weighted Average Exercise Price	$ 269.80	$ 158.20	$ 101.32
Weighted Average Grant Date Fair Value per option	$ 73.14	$ 42.51	$ 30.78
Performance stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance Shares Earned			244,825

Performance Shares Earned

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- Definition

Time based options grant date fair value

+ References

No definition available.

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- Definition

The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

+ References

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- Definition

The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

+ References

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- Definition

The risk-free interest rate assumption that is used in valuing an option on its own shares.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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- Definition

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

+ References

No definition available.

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- Definition

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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- Definition

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

+ References

No definition available.

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- Definition

Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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 (f)(2)(i)
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-URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809

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