Retirement Benefits (Details 4) (United States Postretirement Benefit Plans of US Entity, Defined Benefit [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2011
Before Medicare Subsidy [Member]
Future postretirement health care and life insurance benefit payments
2012	$ 3,247
2013	3,153
2014	3,052
2015	2,945
2016	2,838
2017-2021	12,395
After Medicare Subsidy [Member]
Future postretirement health care and life insurance benefit payments
2012	2,888
2013	2,794
2014	2,700
2015	2,600
2016	2,505
2017-2021	$ 10,956

The amount of the aggregate benefits expected to be paid in the five fiscal years thereafter (the aggregate amount of benefits expected to be paid in years 6 through 10 after the date of the latest statement of financial position).

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph f

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (f)

-URI http://asc.fasb.org/extlink&oid=6962843&loc=d3e1928-114920

Name:	us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsInFiveFiscalYearsThereafter
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant