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Employee Stock and Incentive Plans - Restricted Stock Units (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2011 Restricted Stock Units (RSUs) [Member]		Dec. 31, 2010 Restricted Stock Units (RSUs) [Member]		Dec. 31, 2009 Restricted Stock Units (RSUs) [Member]
Number of Shares [Abstract]
Available as of January 1,			43,803		28,983		0
Granted			20,136		26,589	[1]	30,465	[1]
Awarded					(3,091)		0
Forfeited			(260)		(8,678)		(1,482)
Available as of December 31,			63,464		43,803		28,983
Weighted Average Grant Date Fair Value [Abstract]
As of January 1,			$ 30.61		$ 29.41		$ 0.00
Granted			$ 36.74	[1]	$ 31.83	[1]	$ 29.41	[1]
Awarded			$ 30.30		$ 29.75		$ 0.00
Forfeited			$ 29.41		$ 30.62		$ 29.41
As of December 31,			$ 22.88		$ 30.61		$ 29.41
Restricted Stock Units Granted, Grant Date Fair Value		$ 0.6
Restricted Stock Units Awarded, Shares	100,000		(215)
Restricted Stock Units Awarded, Grant Date Fair Value	$ 0.8	$ 0.1
[1] (a) Shares granted includes accrued dividends.

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Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Awards, Shares

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Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Awards, Weighted Average Grant Date Fair Value (Per Share)

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



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The weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect during the reporting period as a result of the occurrence of a terminating event specified in the contractual agreement of the plan.

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



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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).

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



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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).

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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