Employee Benefit Plans - Summary of plan weighted average asset allocation by asset category along with target allocation for 2012 (Details)	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Percentage of Plan Assets	100.00%	100.00%
Target Allocation for 2013 total percentage	100.00%
Cash and Cash Equivalents \| Retirement Income Plan
Defined Benefit Plan Disclosure [Line Items]
Percentage of Plan Assets	0.20%	0.70%
Target Allocation for 2013 minimum percentage	0.00%
Target Allocation for 2013 maximum percentage	5.00%
Debt Securities - Core Fixed Income \| Retirement Income Plan
Defined Benefit Plan Disclosure [Line Items]
Percentage of Plan Assets	20.20%	23.20%
Target Allocation for 2013 minimum percentage	15.00%
Target Allocation for 2013 maximum percentage	50.00%
Tactical - Fund of Equity and Debt Securities \| Retirement Income Plan
Defined Benefit Plan Disclosure [Line Items]
Percentage of Plan Assets	15.10%	16.30%
Target Allocation for 2013 minimum percentage	10.00%
Target Allocation for 2013 maximum percentage	20.00%
Domestic Equity Securities \| Retirement Income Plan
Defined Benefit Plan Disclosure [Line Items]
Percentage of Plan Assets	15.20%	15.20%
Target Allocation for 2013 minimum percentage	30.00%
Target Allocation for 2013 maximum percentage	50.00%
Global Equity Securities \| Retirement Income Plan
Defined Benefit Plan Disclosure [Line Items]
Percentage of Plan Assets	16.00%	14.80%
Target Allocation for 2013 minimum percentage	10.00%
Target Allocation for 2013 maximum percentage	20.00%
International Equity Securities \| Retirement Income Plan
Defined Benefit Plan Disclosure [Line Items]
Percentage of Plan Assets	15.10%	14.60%
Target Allocation for 2013 minimum percentage	10.00%
Target Allocation for 2013 maximum percentage	20.00%
Real Estate \| Retirement Income Plan
Defined Benefit Plan Disclosure [Line Items]
Percentage of Plan Assets	9.20%	5.60%
Target Allocation for 2013 minimum percentage	0.00%
Target Allocation for 2013 maximum percentage	10.00%
Real Return \| Retirement Income Plan
Defined Benefit Plan Disclosure [Line Items]
Percentage of Plan Assets	9.00%	9.60%
Target Allocation for 2013 minimum percentage	0.00%
Target Allocation for 2013 maximum percentage	10.00%
Other \| Retirement Income Plan
Defined Benefit Plan Disclosure [Line Items]
Percentage of Plan Assets	0.00%	0.00%
Target Allocation for 2013 minimum percentage	0.00%
Target Allocation for 2013 maximum percentage	5.00%

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Target allocation of investments of this type to total plan assets presented on a weighted average basis.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (d)(i)

-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 5

-Subparagraph (c)(i)

-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e2446-114920

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- Definition

Target allocation maximum percentage of investments of this type to total plan assets presented on a weighted average basis.

+ References

+ Details

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- Definition

Target allocation minimum percentage of investments of this type to total plan assets presented on a weighted average basis.

+ References

+ Details

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- Definition

Percentage of fair value of investments (categorized by debt securities, equity securities, real estate and other plan assets) to the fair value of plan assets held.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 5

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e2446-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (d)(1)

-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph d(1)

-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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