Stock-Based Compensation - Employee Stock Purchase Plan Activity (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
EMC Employee Stock Purchase - 1989 Plan | Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash proceeds	$ 186	$ 82	$ 154
Common shares purchased	8	4	7
Weighted-average price per share	$ 22.44	$ 20.08	$ 21.65
VMware | VMware Employee Stock Purchase - 2007 Plan | VMware Class A common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash proceeds	$ 80	$ 76	$ 69
Common shares purchased	1	1	1
Weighted-average price per share	$ 73.21	$ 65.97	$ 77.34