Earnings (Loss) per Share Level 4 (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended	12 Months Ended
Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net Income (Loss) Attributable to Parent [Abstract]
Income (Loss) from Continuing Operations Attributable to Parent									$ 896	$ 1,673	$ 1,349
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	$ 0	$ 0	$ 0	$ 0	$ 0	$ 9	$ 0	$ 0	0	9	(551)
Net Income (Loss) Attributable to Parent									$ 896	$ 1,682	$ 798
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Weighted Average Number of Shares Outstanding, Basic	376.6	383.8	391.8	398.5	406.9	413.8	418.7	422.6	387.7	415.5	441.8
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements									3.5	5.0	12.1
Incremental Common Shares Attributable to Dilutive Effect of Call Options and Warrants									3.6	4.7	6.3
Weighted Average Number of Shares Outstanding, Diluted	383.8	390.5	398.6	406.3	415.9	423.0	428.1	433.7	394.8	425.2	460.2
Earnings Per Share, Basic and Diluted [Abstract]
Income (Loss) from Continuing Operations, Per Basic Share									$ 2.31	$ 4.03	$ 3.05
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share									0.00	0.02	(1.24)
Earnings Per Share, Basic	$ (0.22)	$ 1.14	$ 0.55	$ 0.81	$ 1.03	$ 0.92	$ 0.99	$ 1.11	2.31	4.05	1.81
Income (Loss) from Continuing Operations, Per Diluted Share									2.27	3.93	2.93
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share									0.00	0.03	(1.20)
Earnings Per Share, Diluted	$ (0.22)	$ 1.12	$ 0.54	$ 0.79	$ 1.01	$ 0.90	$ 0.96	$ 1.08	$ 2.27	$ 3.96	$ 1.73

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 55
-Paragraph 52
-URI http://asc.fasb.org/extlink&oid=65016374&loc=d3e4984-109258

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(19))
-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64863997&loc=d3e1252-109256

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(21))
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(23))
-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882