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Retirement Plans (Schedule of Alternative Investment Portfolio by Strategy and Remaining Commitment) (Details) (USD $) In Thousands, unless otherwise specified | Dec. 31, 2011 | Dec. 31, 2010
--- | --- | ---
Other investments | $ 128,301 | $ 137,865
Alternative Investments [Member] |  |
Other investments | 124,548 | 135,110
Remaining Commitment | 55,344 |
Alternative Investments [Member] | Private Equity [Member] |  |
Other investments | 21,736 | 21,601
Remaining Commitment | 5,368 |
Alternative Investments [Member] | Real Estate Strategy [Member] |  |
Other investments | 13,767 | 14,192
Remaining Commitment | 10,569 |
Retirement Income Plan [Member] | Alternative Investments [Member] |  |
Other investments | 17,000 | 19,000
Remaining Commitment | 4,800 |
Retirement Income Plan [Member] | Alternative Investments [Member] | Private Equity [Member] |  |
Other investments | 12,600 | 14,500
Remaining Commitment | 4,200 |
Retirement Income Plan [Member] | Alternative Investments [Member] | Equity Long Short Hedge [Member] |  |
Other investments | 1,800 | 1,800
Remaining Commitment | 0 |
Retirement Income Plan [Member] | Alternative Investments [Member] | Real Estate Strategy [Member] |  |
Other investments | 2,600 | 2,700
Remaining Commitment | $ 600 |

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- Definition Other investments not otherwise specified in the taxonomy. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.1(f,g)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 12 -Article 5 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 7 -Section 03 -Paragraph 1 -Subparagraph g Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.12) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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