Litigation, Investigations and Claims (Unaudited) Litigation (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2012	Dec. 31, 2007	Dec. 31, 2011
Loss Contingencies [Line Items]
Transition period, pension benefit, employer-funded portion	5 years
Contract award		$ 875
Receivables, unpaid long-term contracts	3,231		2,964
Claims asserted, range of possible loss	748
United States Postal Service
Loss Contingencies [Line Items]
Gain contingency, unrecorded amount	179
Receivables, unpaid long-term contracts	63
United States Postal Service
Loss Contingencies [Line Items]
Claims asserted, range of possible loss	$ 341