Basis of Presentation and Significant Accounting Policies - Schedule of Revenues from Third Party Payers and Uninsured (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 9,279	$ 8,469	$ 18,204	$ 16,959
Uninsured	318	693	706	1,092
Other	361	311	731	616
Revenues before provision for doubtful accounts	9,958	9,473	19,641	18,667
Provision for doubtful accounts	(728)	(1,023)	(1,579)	(1,777)
Revenues	9,230	8,450	18,062	16,890
Revenues from third party payers, Ratio	100.60%	100.20%	100.80%	100.40%
Uninsured, Ratio	3.40%	8.20%	3.90%	6.50%
Other, Ratio	3.90%	3.70%	4.00%	3.60%
Revenues before provision for doubtful accounts, Ratio	107.90%	112.10%	108.70%	110.50%
Revenues before provision for doubtful accounts, Ratio	107.90%	112.10%	108.70%	110.50%
Provision for doubtful accounts, Ratio	(7.90%)	(12.10%)	(8.70%)	(10.50%)
Revenues ratio from third party payers	100.00%	100.00%	100.00%	100.00%
Medicare [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	2,040	1,976	4,165	4,114
Revenues from third party payers, Ratio	22.10%	23.40%	23.10%	24.40%
Managed Medicare [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	906	804	1,805	1,647
Revenues from third party payers, Ratio	9.80%	9.50%	10.00%	9.80%
Medicaid [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	588	365	1,032	697
Revenues from third party payers, Ratio	6.40%	4.30%	5.70%	4.10%
Managed Medicaid [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	452	378	873	779
Revenues from third party payers, Ratio	4.90%	4.50%	4.80%	4.60%
Managed Care and Other Insurers [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	4,959	4,655	9,669	9,141
Revenues from third party payers, Ratio	53.80%	55.10%	53.50%	54.10%
International (Managed Care and Other Insurers) [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 334	$ 291	$ 660	$ 581
Revenues from third party payers, Ratio	3.60%	3.40%	3.70%	3.40%