Related Parties (Details) (Director [Member], USD $)	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2011
Related Party Transaction [Line Items]
Related Party Transaction Amount of Assets Under Management in Defined Benefit Plans	$ 105,900,000	$ 105,900,000
Related Party Transaction Amount of Assets in Defined Contributions Plans	19,400,000	19,400,000
Related Party Transaction Percent of Assets in Defined Contribution Plan Assets	6.40%	6.40%
Defined Benefit Pension [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	0.1	100,000
Trinity [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction	110,900,000	110,900,000
Related Party Transaction, Expenses from Transactions with Related Party	$ 100,000	$ 200,000

Expenses recognized during the period resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party during the period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 57
-Paragraph 2
-Subparagraph c
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

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Amounts Invested in Defined Contribution Plan Mutual Fund Managed by a Director's Investment Advisory Firm

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