Changes in Accounting Principle (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	1 Months Ended	3 Months Ended
	Jan. 31, 2012	Mar. 31, 2012
Changes in Accounting Principle
Percentage of consolidated inventories affected by change in accounting principle		51.00%
Change in methods of valuing prescription drug inventories
Effect of changes in accounting principle
Decrease in inventories	$ 146
Increase in current deferred income tax assets	57
Decrease in retained earnings	89
Decrease in diluted earnings per common share		$ 0.01
Decrease in income from continuing operations and net income attributable to CVS Caremark		$ 19
Decrease in basic earnings per common share		$ 0.01