Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Antidilution
-URI http://asc.fasb.org/extlink&oid=6505113

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Diluted Earnings Per Share
-URI http://asc.fasb.org/extlink&oid=6510752

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Contingent Stock Agreement
-URI http://asc.fasb.org/extlink&oid=6508534

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Earnings (Loss) Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income (Loss) (Numerator):
Net income (loss)	$ 338	$ 205	$ 143	$ 192	$ 188	$ 188	$ 193	$ 203	$ 878	$ 772	$ (239)
Earnings applicable to non-vested restricted stock									0	0	0
Net income (loss) applicable to common stock for computing basic earnings (loss) per common share									878	772	(239)
Net income (loss) as adjusted for purposes of computing diluted earnings (loss) per common share									$ 878	$ 772	$ (239)
Weighted average number of shares:
Weighted average shares outstanding for computing basic earnings (loss) per common share (in shares)									554,278	568,435	600,892
Incremental common shares attributable to dilutive securities:
Number of shares as adjusted for purposes of computing diluted earnings (loss) per common share (in shares)									555,093	569,739	600,892
Basic earnings (loss) per common share (in dollars per share)	$ 0.62	$ 0.37	$ 0.26	$ 0.34	$ 0.33	$ 0.33	$ 0.34	$ 0.35	$ 1.58	$ 1.36	$ (0.40)
Diluted earnings (loss) per common share (in dollars per share)	$ 0.62	$ 0.37	$ 0.26	$ 0.34	$ 0.33	$ 0.33	$ 0.34	$ 0.35	$ 1.58	$ 1.36	$ (0.40)
Number of shares of common stock excluded from the computation of diluted earnings per share									3,100	2,500	2,700
Share-based payments and convertible debt securities
Incremental common shares attributable to dilutive securities:
Number of shares of common stock excluded from the computation of diluted earnings per share											1,300
Common Class A
Weighted average number of shares:
Outstanding during period (in shares)									559,260	572,748	604,404
Non-vested restricted stock (in shares)									(4,982)	(4,313)	(3,512)
Weighted average shares outstanding for computing basic earnings (loss) per common share (in shares)									554,278	568,435	600,892
Incremental common shares attributable to dilutive securities:
Shares issuable under convertible securities (in shares)									10	10	0
Shares issuable under incentive compensation plans (in shares)									805	1,294	0
Number of shares as adjusted for purposes of computing diluted earnings (loss) per common share (in shares)									555,093	569,739	600,892