Accounting Policies - Schedule of Revenues from Third Party Payers and Uninsured (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenues [Line Items]
Revenues from third party payers									$ 33,272	$ 29,846	$ 28,038
Uninsured									2,580	1,846	1,732
Other									931	814	913
Revenues before provision for doubtful accounts									36,783	32,506	30,683
Provision for doubtful accounts									(3,770)	(2,824)	(2,648)
Revenues	8,434	8,062	8,112	8,405	7,769	7,258	7,249	7,406	33,013	29,682	28,035
Revenues from third party payers, ratio									100.70%	100.60%	100.10%
Uninsured Ratio									7.80%	6.20%	6.20%
Other Ratio									2.80%	2.70%	3.30%
Revenues before provision for doubtful accounts, ratio									111.30%	109.50%	109.60%
Provision for doubtful accounts Ratio									(11.30%)	(9.50%)	(9.60%)
Revenues ratio from third party payers									100.00%	100.00%	100.00%
Medicare [Member]
Revenues [Line Items]
Revenues from third party payers									8,292	7,653	7,203
Revenues from third party payers, ratio									25.10%	25.80%	25.70%
Managed Medicare [Member]
Revenues [Line Items]
Revenues from third party payers									2,954	2,442	2,162
Revenues from third party payers, ratio									8.90%	8.20%	7.70%
Medicaid [Member]
Revenues [Line Items]
Revenues from third party payers									1,464	1,845	1,962
Revenues from third party payers, ratio									4.40%	6.20%	7.00%
Managed Medicaid [Member]
Revenues [Line Items]
Revenues from third party payers									1,504	1,265	1,165
Revenues from third party payers, ratio									4.60%	4.30%	4.20%
Managed care and other insurers [Member]
Revenues [Line Items]
Revenues from third party payers									17,998	15,703	14,762
Revenues from third party payers, ratio									54.50%	52.90%	52.70%
International (managed care and other insurers) [Member]
Revenues [Line Items]
Revenues from third party payers									$ 1,060	$ 938	$ 784
Revenues from third party payers, ratio									3.20%	3.20%	2.80%