Borrowings (Credit Facilities Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Line of Credit Facility [Line Items]
CSC’s stockholders’ equity, excluding accumulated other comprehensive income	$ 13,500,000,000
Commercial paper [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	1,500,000,000
Commercial Paper Notes, amount outstanding	0	$ 0
Standby letters of credit [Member]
Line of Credit Facility [Line Items]
Line of credit facility, current borrowing capacity	304,000,000
Group of banks facility [Member] | Line of credit [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 750,000,000
Unsecured credit facility, expiration date	Jun. 01, 2016
Minimum level of stockholders' equity required under credit facility	$ 8,900,000,000
Line of credit	0	0
Group of banks [Member] | Line of credit [Member]
Line of Credit Facility [Line Items]
Line of credit	0	0
Group of banks [Member] | Standby letters of credit [Member]
Line of Credit Facility [Line Items]
Line of credit	0	$ 0
Group of banks [Member] | Charles Schwab & Co., Inc. [Member] | Standby letters of credit [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 295,000,000
Maximum [Member] | Commercial paper [Member]
Line of Credit Facility [Line Items]
Debt instrument term	270 days