Earnings Per Share - Common Share Data Used for Computing Basic and Diluted Earnings Per Share (Detail) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Earnings Per Share [Abstract]
Number of common shares outstanding at end of period	465.9	468.1	465.9	468.1
Effect of using weighted average common shares outstanding		(0.2)	(0.3)	(1.3)
Weighted average basic common shares outstanding	465.9	467.9	465.6	466.8
Dilutive effect of equity-based compensation awards and other contingently issuable shares	2.1	1.5	1.9	1.3
Weighted average diluted common shares outstanding	468.0	469.4	467.5	468.1
Potentially issuable shares	13.8	13.6	13.8	13.6
Number of anti-dilutive potentially issuable shares excluded from diluted common shares outstanding	0.8	1.2	2.8	3.2