Retirement Plans (Details Textual) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2012
Retirement Plans (Textual) [Abstract]
Corporation expects to contribute to its pension plans 2012	$ 150
Corporation contributed to its pension plans	$ 50

The employer's best estimate, as soon as it can be reasonably determined, of contributions expected to be paid to the plan in the current remaining fiscal period. Estimated contributions may be presented in the aggregate combining (1) contributions required by funding regulations or laws, (2) discretionary contributions, and (3) noncash contributions.

No definition available.

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