Long-Term Incentive Employee Compensation Rollforward of Outstanding Restricted Stock (Detail) - RSUs, PSUs and RSAs [Member] - $ / shares shares in Millions	12 Months Ended
	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Beginning Outstanding, shares	1.3		1.1		1.3
Granted , shares	0.5		0.5		0.4
Performance Adjustment, shares	(0.1)	[1]	0.1	[1]	0.0
Lapsed, shares	(0.5)		(0.3)		(0.5)
Cancelled, shares	(0.1)		(0.1)		(0.1)
Ending Outstanding, shares	1.1		1.3		1.1
Performance Units Vested Not Yet Issued	0.0		0.3		0.0
Outstanding, Weighted Average Grant Date Fair Value	$ 36.56		$ 31.70		$ 24.17
Granted, Weighted Average Grant Date Fair Value	33.28		41.34		43.88
Performance Adjustment, Weighted Average Grant Date Fair Value	45.47		29.59		0
Lapsed, Weighted Average Grant Date Fair Value	29.86		24.09		21.62
Canceled, Weighted Average Grant Date Fair Value	39.20		35.89		27.33
Outstanding, Weighted Average Grant Date Fair Value	38.24		36.56		31.70
Weighted Average Grant Date Fair Value of Performance Units Vested Not Yet Issued	$ 0		$ 29.59		$ 0

[1] (a)Represents the adjustment to the number of shares to be issued above or below target for performance results achieved relative to PSUs granted in 2014 that vested on December 31, 2016 and PSUs granted in 2013 that vested on December 31, 2015.