Long-term Incentive Compensation Plans (Details) (USD $) Share data in Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Long-term Incentive Compensation Plans [Abstract]
Holding units purchased in period (in units)	0.7	0.2
Dollar amount paid for holding units acquired	$ 17,000,000	$ 3,700,000
Open-market purchases of holding units (in units)	0.6
Dollar amount paid for open-market purchases of holding units	15,100,000us-gaap_PaymentsForRepurchaseOfEquity
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units issued upon options exercised (in units)	0.2
Proceeds from stock options exercised	$ 3,901,000	$ 4,656,000
Employees and Eligible Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted holding unit awards to employees (in units)	0.1	0.2

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The cash outflow to reacquire common and preferred stock.

+ References

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- Definition

The cash inflow associated with the amount received from holders exercising their stock options. This item inherently excludes any excess tax benefit, which the entity may have realized and reported separately.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 14

-Subparagraph (a)

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- Definition

The number of shares purchased on the open market during the period for issuance to employees under the 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

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-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901

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- Definition

Gross number of shares (or other type of equity) issued during the period as a result of any equity-based compensation plan other than an employee stock ownership plan (ESOP). Shares issued could result from the issuance of restricted stock, the exercise of stock options, stock issued under employee stock purchase plans, and/or other employee benefit plans.

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No definition available.

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- Definition

Number of share options (or share units) exercised during the current period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

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-Topic 505

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-Name Accounting Standards Codification

-Topic 210

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-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.28,29)

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-Paragraph 2

-Subparagraph (c)(1)(iv)(2)

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 29, 30

-Article 5

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- Definition

Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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Equity impact of the value of stock that has been repurchased during the period and has not been retired and is not held in treasury. Some state laws may mandate the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

+ References

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