Income Tax (Narrative - Unrecognized Tax Benefits) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 182	$ 240	$ 84
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	1	2	1
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	5	7	7
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	$ 180