Compensation Plans Compensation Plans: Postretirement Benefits (Details) (Defined Contribution Pension [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Defined Contribution Pension [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Deferred Compensation Arrangement With Individual, Maximum Employee Deferral	60.00%
Deferred Compensation Arrangement with Individual, Employer Match, Maximum Percentage	6.00%
Deferred Compensation Arrangement with Individual, Employer Contribution	$ 2.9	$ 2.5	$ 2.5

The amount of payment into the fund established for purposes of making future disbursements to the individual in accordance with the terms and understanding of the deferred compensation arrangement.

No definition available.

Name:	us-gaap_DeferredCompensationArrangementWithIndividualEmployerContribution
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration