Benefit Plans Benefit Plans - Future Benefit Payments (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2012
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
2013	$ 24,741
2014	27,556
2015	28,051
2016	29,662
2017	31,147
2018-2022	183,750
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year [Abstract]
Amount of net prior service cost (credit)	258
Amount of net loss	21,377
Other Postretirement Benefit Plans, Defined Benefit [Member]
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year [Abstract]
Amount of net prior service cost (credit)	(488)
Amount of net loss	422
Other Benefits before Medicare Part D
Defined Benefit Plan Disclosure [Line Items]
2013	1,798
2014	1,771
2015	1,716
2016	1,660
2017	1,600
2018-2022	6,773
Other Benefits after Medicare Part D Subsidy
Defined Benefit Plan Disclosure [Line Items]
2013	1,607
2014	1,585
2015	1,532
2016	1,484
2017	1,432
2018-2022	$ 6,076

The amounts in accumulated other comprehensive income related to gains and losses that are not recognized immediately and are expected to be recognized as components of net periodic benefit cost over the next fiscal year that follows the most recent annual statement of financial position presented.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (s)

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

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 158

-Paragraph 7

-Subparagraph d

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph s

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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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