Commitments and Contingencies Level 4 (Details) - Annual Purchase Commitments (USD $)
In Millions, unless otherwise specified
Dec. 31, 2014
Long-term Purchase Commitment [Line Items]  
P2015Y $ 276
P2016Y 287
P2017Y 61
P2018Y 53
P2019Y 53
2020 and beyond 160
Total minimum payments 890
Less: Amount representing interest (64)
Present Value of Minimum Payments $ 826