Earnings (Loss) Per Common Share Level 4 (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Net Income (Loss) Attributable to Parent [Abstract]
Net Income (Loss) Attributable to Parent	$ 216	$ 413	$ 539	$ 880
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Weighted Average Number of Shares Outstanding, Basic	391.8	418.7	395.2	420.6
Incremental Common Shares Attributable to Dilutive Effect of Call Options and Warrants	3.6	5.0	3.6	5.3
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	3.2	4.4	3.6	5.0
Weighted Average Number of Shares Outstanding, Diluted	398.6	428.1	402.4	430.9
Earnings Per Share, Basic and Diluted [Abstract]
Earnings Per Share, Basic	$ 0.55	$ 0.99	$ 1.36	$ 2.09
Earnings Per Share, Diluted	$ 0.54	$ 0.96	$ 1.34	$ 2.04