Common Equity - Share-Based Compensation Plans (Details)	9 Months Ended
Sep. 30, 2016 $ / shares shares
Stock options
Stock-based Compensation Plans
Stock options granted \| shares	794,764
Stock options granted, weighted average exercise price (in dollars per share) \| $ / shares	$ 52.15
Stock options granted, weighted-average grant date fair value (in dollars per share) \| $ / shares	$ 5.14
Restricted shares
Stock-based Compensation Plans
Awards granted, other than stock options \| shares	146,941
Weighted average grant date fair value, awards other than stock options (in dollars per share) \| $ / shares	$ 53.69
Performance units
Stock-based Compensation Plans
Awards granted, other than stock options \| shares	297,397

The number of grants made 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).

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=6415400&loc=d3e5070-113901

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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

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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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- Definition

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

+ References

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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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (d)(1)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

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

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