Equity Arrangements - Additional Information (Detail) - USD ($)				1 Months Ended				3 Months Ended					9 Months Ended		12 Months Ended
	Nov. 17, 2016	Feb. 01, 2016	Oct. 31, 2014	Oct. 29, 2016	Mar. 31, 2015	Feb. 28, 2015	Dec. 31, 2013	Sep. 30, 2017	Jul. 01, 2017	Dec. 31, 2016	Oct. 01, 2016	Apr. 02, 2016	Sep. 30, 2017	Oct. 01, 2016	Dec. 31, 2016	Dec. 28, 2013	May 17, 2017	May 11, 2017
Stockholders Equity Note [Line Items]
Interest Expense								$ 1,300,000
Forward share purchase contract			$ 150,000,000	$ 147,400,000	$ 350,000,000
Payments for Repurchase of Common Stock								$ 600,000			$ 600,000		$ 16,200,000	$ 362,700,000	$ 374,100,000
Common Stock, Shares, Issued	3,504,165							176,902,738		176,902,738			176,902,738		176,902,738
Long-term Debt								$ 750,000,000		$ 345,000,000	$ 345.0
Number of common shares purchased under call option													4,600,000			3,500,000
Call option, aggregate premium							$ 9,700,000		$ 25,100,000				$ 25,100,000
Preferred Stock, Value, Issued								$ 750,000,000		$ 0			$ 750,000,000		$ 0
Equity Forward Contracts, Net Settlement, Shares					3,645,510
Option Indexed to Issuer's Equity, Settlement Alternatives, Shares, at Fair Value		293,142	1,603,822			911,077		418,234		711,376			418,234		711,376
Equity Units Conversion Rate Number Of Common Stock Shares								0.7244	0.7241
Stock Issued During Period, Value, Treasury Stock Reissued	$ 98.45
Treasury Stock Acquired, Average Cost Per Share		$ 94.34				$ 96.46					$ 117.84
Document Period End Date													Sep. 30, 2017
Treasury Stock, Shares, Acquired															3,940,087
equity units issued									7,500,000
Equity Unit									$ 750,000,000							$ 345,000,000
Shares Issued, Price Per Share								$ 138.05	$ 100				$ 138.05					$ 138.10
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share								100	100	$ 0
Preferred Stock, Liquidation Preference Per Share								1,000	$ 1,000				1,000
equity unit proceeds									$ 727,500,000
Preferred Stock, Shares Issued									750,000
Preferred Stock, Liquidation Preference, Value									$ 750,000,000
Preferred Stock Conversion Rate Number Of Common Stock Shares								6.1649	$ 6.1627
Option Indexed to Issuer's Equity, Strike Price								$ 162.21	162.27				$ 179.47
Forward Contract Indexed to Issuer's Equity, Shares								5,400,000
Option Indexed to Issuer's Equity, Settlement Alternatives, Cash, at Fair Value								$ 28,200,000					$ 28,200,000
Percentage Of Contract Price Paid								5.375%					5.375%
Forward Contract Indexed to Issuer's Equity, Settlement Alternatives, Cash, at Fair Value								$ 107,500,000					$ 107,500,000				$ 116,900,000
Call Option [Member]
Stockholders Equity Note [Line Items]
Call option, average price (in dollars per share)								$ 5.43								$ 2.77
Maximum [Member]
Stockholders Equity Note [Line Items]
Option Indexed to Issuer's Equity, Strike Price								179.47	179.53
Minimum [Member]
Stockholders Equity Note [Line Items]
Option Indexed to Issuer's Equity, Strike Price								$ 162.21	$ 162.27
Common Stock [Member]
Stockholders Equity Note [Line Items]
Equity Units Conversion Rate Number Of Common Stock Shares	1.0157
Common Stock [Member] | Maximum [Member]
Stockholders Equity Note [Line Items]
Payments for Repurchase of Common Stock																$ 80.65
Equity Units Conversion Rate Number Of Common Stock Shares															1.2399	1.2399
Common Stock [Member] | Minimum [Member]
Stockholders Equity Note [Line Items]
Payments for Repurchase of Common Stock																$ 98.80
Equity Units Conversion Rate Number Of Common Stock Shares															1.0122	1.0122
Call Option [Member]
Stockholders Equity Note [Line Items]
Number of common shares purchased under call option		3,100,000.0										9,100,000.0				12,200,000.0