Taxes on Income (Temporary Differences That Created Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Employee compensation, severance, and benefits	$ 133	$ 216
Net unrealized loss on available for sale securities	57	97
Reserves and allowances	15	25
Facilities lease commitments	14	25
State and local taxes	12	17
Net operating loss carryforwards	5	5
Other	3	0
Total deferred tax assets	239	385
Valuation allowance	(2)	(3)
Deferred tax assets — net of valuation allowance	237	382
Deferred tax liabilities:
Capitalized internal-use software development costs	(89)	(118)
Depreciation and amortization	(72)	(114)
Other	0	(7)
Total deferred tax liabilities	(161)	(239)
Deferred tax asset – net	$ 76	$ 143