Changes in Outstanding SARs (Detail) - Stock Appreciation Rights shares in Millions	12 Months Ended
	Dec. 31, 2015 $ / shares shares
Number of SARs (in millions)
Outstanding beginning balance | shares	5.8
Granted | shares	0.3
Exercised | shares	(0.5)
Forfeited | shares	0.0
Outstanding ending balance | shares	5.6
Weighted Average Exercise Price
Outstanding beginning balance (per unit) | $ / shares	$ 33
Granted (per unit) | $ / shares	83
Exercised (in shares) | $ / shares	34
Forfeited (per unit) | $ / shares	76
Outstanding ending balance (per unit) | $ / shares	$ 36