Stock-based Compensation Plans - Stock Option and SARs Activities (Detail) - Stock Appreciation Rights (SARs) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Beginning Balance, Shares	1,966,549	2,582,074	3,433,362
Granted, Shares		1,104	470,617
Exercised, Shares	(427,598)	(616,563)	(1,269,323)
Expired/forfeited, Shares	(27,974)	(66)	(52,582)
Ending Balance, Shares	1,510,977	1,966,549	2,582,074
Beginning Balance, Weighted Average Exercise Price	$ 59.80	$ 56.36	$ 52.52
Granted, Weighted Average Exercise Price		81.74	75.82
Exercised, Weighted Average Exercise Price	45.67	45.45	53.24
Expired/forfeited, Weighted Average Exercise Price	63.10	46.44	53.56
Ending Balance, Weighted Average Exercise Price	$ 63.73	$ 59.80	$ 56.36