Accounting Policies - Schedule of Estimated Cost of Uncompensated Care (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accounting Policies [Abstract]
Patient care costs (salaries and benefits, supplies, other operating expenses and depreciation and amortization)	$ 31,478	$ 29,606	$ 28,533
Cost-to-charges ratio (patient care costs as percentage of gross patient charges)	15.50%	16.30%	17.20%
Total uncompensated care	15,943	15,565	13,841
Multiply by the cost-to-charges ratio	15.50%	16.30%	17.20%
Estimated cost of total uncompensated care	$ 2,471	$ 2,537	$ 2,381