Computation of Basic/Diluted Earnings Per Common Share (Details) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Unvested restricted stock units participating in earnings (in shares)	0	2	0	3
Performance shares not included in dilutive shares (performance measures not yet met)	9	10	8	10
Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	1	1	1	4