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.

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
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-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 28A
-URI http://asc.fasb.org/extlink&oid=64863997&loc=d3e1500-109256

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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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%