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Share-Based Payments (Details 5) - Market stock units - USD ($) | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Assumptions used in valuation of market based stock units |  |  |  |
Expected dividend yield | 0.00% |  | 0.00% | 0.00%
Minimum range of risk-free interest rates | 0.90% |  | 0.60% | 0.20%
Maximum range of risk-free interest rates | 1.60% |  | 0.90% | 1.00%
Average stock price on grant date minimum | $ 263.18 |  | $ 260.67 | $ 227.35
Average stock price on grant date maximum | $ 267.88 |  | $ 304.86 | $ 426.27
Weighted average grant date fair value | $ 382.59 | [1] | $ 328.03 | $ 493.43
Minimum |  |  |  |
Assumptions used in valuation of market based stock units |  |  |  |
Range of expected stock price volatility | 33.00% |  | 38.20% | 31.00%
Maximum |  |  |  |
Assumptions used in valuation of market based stock units |  |  |  |
Range of expected stock price volatility | 35.60% |  | 40.70% | 33.20%
[1] | MSUs granted in 2017 include approximately 9,000 MSUs issued in 2017 based upon the attainment of performance criteria set for 2013, in relation to awards granted in that year. MSUs granted during 2017 also include awards granted in conjunction with our annual awards made in February 2017 and MSUs granted in conjunction with the hiring of employees. These grants reflect the target number of shares eligible to be earned at the time of grant. MSUs granted in 2017 reflect an adjustment based upon the final performance multiplier in relation to shares granted in 2016, 2015 and 2014.

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- Definition Average stock price on grant date in dollars minimum. + References No definition available. + Details
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- Definition Valuation of granted stock units. + References No definition available. + Details
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- Definition 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 Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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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 Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(iii) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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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 Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(ii) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition The maximum risk-free interest rate assumption that is used in valuing an option on its own shares. + References No definition available. + Details
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