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Employee Share-Based Incentive Compensation Plans (WTM Non-Qualified and Qualified Options) (Details) - USD ($) $ / shares in Units, $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Share-based compensation arrangement by share-based payment award |  |  |
Incremental common shares attributable to share-based payment arrangements | 3,217 |  |
Shares Issued, Price Per Share | $ 742 |  |
Qualified Plan [Member] |  |  |
Share-based compensation arrangement by share-based payment award |  |  |
Percentage of common shares outstanding | 3.00% | 3.00% |
Eligible contribution percentage | 3.00% | 3.00% | 2.00%
Chief Executive Officer |  |  |
Share-based compensation arrangement by share-based payment award |  |  |
Shares Issued, Price Per Share | $ 742 |  |
Employee Stock Option [Member] |  |  |
Share-based compensation arrangement by share-based payment award |  |  |
Incremental common shares attributable to share-based payment arrangements | 40,000 | 125,000 |
Employee Stock Option [Member] | Chief Executive Officer |  |  |
Share-based compensation arrangement by share-based payment award |  |  |
Incremental common shares attributable to share-based payment arrangements | 40,000 | 125,000 |
Employee Stock Option [Member] | Combination One |  |  |
Share-based compensation arrangement by share-based payment award |  |  |
Incremental common shares attributable to share-based payment arrangements | 5,000 |  |
Shares Issued, Price Per Share | $ 742 |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value | $ 0.4 |  |
Employee Stock Option [Member] | Combination Two [Member] |  |  |
Share-based compensation arrangement by share-based payment award |  |  |
Incremental common shares attributable to share-based payment arrangements | 80,000 |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value | $ 8.4 |  |
Common Stock |  |  |
Share-based compensation arrangement by share-based payment award |  |  |
Incremental common shares attributable to share-based payment arrangements | 9,930 |  |
Long Term Incentive Plan | Range Of Performance Cycle From 2013 to 2015 [Member] |  |  |
Share-based compensation arrangement by share-based payment award |  |  |
Percentage of payout for minimum growth target percentage | 24.30% |  |

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- Definition Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 28A -URI http://asc.fasb.org/extlink&oid=64863997&loc=d3e1500-109256 + Details
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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. + References No definition available. + Details
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- Definition Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Per share or per unit amount of equity securities issued. + References No definition available. + Details
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- Definition Represents the variable contribution amounts earned by eligible participants of the KSOP as a percentage of salary. + References No definition available. + Details
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- Definition Represents the percentage of total common shares outstanding owned by the plans. + References No definition available. + Details
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- Definition Represents the lpercentage of target achieved, low end of range. + References No definition available. + Details
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