Taxes on Income (Reconciliation of Federal Statutory Income Tax Rate to Effective Income Tax Rate) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Taxes on Income [Abstract]
Federal statutory income tax rate	35.00%		35.00%		35.00%
State income taxes, net of federal tax benefit	2.30%	[1]	2.30%	[1]	1.20%	[1]
Other	0.20%		(0.10%)		(0.20%)
Effective income tax rate	37.50%		37.20%		36.00%
Impact of non recurring state tax benefits			$ 4		$ 20

[1] Includes the impact of a non-recurring state tax benefit of which $4 million and $20 million were recorded in 2013 and 2012, respectively.