Financial Instruments and Fair Value Measurements - Foreign Currency Contracts Activity (Detail)		12 Months Ended
		Dec. 31, 2017 USD ($) Derivative CAD / $ £ / $ € / $ ¥ / $		Dec. 31, 2017 GBP (£) Derivative CAD / $ £ / $ € / $ ¥ / $	Dec. 31, 2017 JPY (¥) Derivative CAD / $ £ / $ € / $ ¥ / $	Dec. 31, 2017 CAD Derivative CAD / $ £ / $ € / $ ¥ / $	Dec. 31, 2017 EUR (€) Derivative CAD / $ £ / $ € / $ ¥ / $	Dec. 31, 2016 USD ($)		Dec. 31, 2016 GBP (£)	Dec. 31, 2016 JPY (¥)	Dec. 31, 2016 CAD	Dec. 31, 2016 EUR (€)	Dec. 31, 2015 USD ($)		Dec. 31, 2015 GBP (£)	Dec. 31, 2015 JPY (¥)	Dec. 31, 2015 CAD	Dec. 31, 2015 EUR (€)
Net Investment Hedges [Member] | CAD
Derivative [Line Items]
Notional amounts at January 1		$ 100,000,000				CAD 133,000,000		$ 0				CAD 0		$ 0				CAD 0
New contracts		99,000,000				133,000,000		100,000,000				133,000,000		298,000,000				394,000,000
Matured, expired or settled contracts		(100,000,000)				(133,000,000)		0				0		(298,000,000)				(394,000,000)
Notional amounts at December 31		$ 99,000,000				CAD 133,000,000		100,000,000				133,000,000		0				CAD 0
Weighted average forward rate at December 31 | CAD / $		1.34		1.34	1.34	1.34	1.34
Active contracts at December 31		2		2	2	2	2
Net Investment Hedges [Member] | GBP [Member]
Derivative [Line Items]
Notional amounts at January 1		$ 46,000,000		£ 31,000,000				386,000,000		£ 238,000,000				400,000,000		£ 238,000,000
New contracts		127,000,000		100,000,000				131,000,000		90,000,000				186,000,000		118,000,000
Matured, expired or settled contracts		(173,000,000)		(131,000,000)				(471,000,000)		(297,000,000)				(200,000,000)		(118,000,000)
Notional amounts at December 31		$ 0		£ 0				46,000,000		31,000,000				386,000,000		238,000,000
Weighted average forward rate at December 31 | £ / $		0		0	0	0	0
Active contracts at December 31		0		0	0	0	0
Net Investment Hedges [Member] | JPY
Derivative [Line Items]
Notional amounts at January 1		$ 0			¥ 0			0			¥ 0			250,000,000			¥ 24,136,000,000
New contracts								99,000,000			11,189,000,000			353,000,000			43,373,000,000
Matured, expired or settled contracts								(99,000,000)			(11,189,000,000)			(603,000,000)			(67,509,000,000)
Notional amounts at December 31								0			0			0			0
Net Investment Hedges [Member] | EUR
Derivative [Line Items]
Notional amounts at January 1								0					€ 0	400,000,000					€ 300,000,000
New contracts														0					0
Matured, expired or settled contracts														(400,000,000)					(300,000,000)
Notional amounts at December 31														0					0
Forwards and Options [Member] | CAD
Derivative [Line Items]
Notional amounts at January 1		38,000,000	[1]			CAD 50,000,000
New contracts		41,000,000	[1]			52,000,000
Matured, expired or settled contracts		(23,000,000)	[1]			(30,000,000)
Notional amounts at December 31		$ 56,000,000	[1]			CAD 72,000,000		38,000,000	[1]			CAD 50,000,000
Weighted average forward rate at December 31 | CAD / $		1.29		1.29	1.29	1.29	1.29
Active contracts at December 31		24		24	24	24	24
Forwards and Options [Member] | GBP [Member]
Derivative [Line Items]
Notional amounts at January 1		$ 78,000,000	[1]	£ 48,000,000				148,000,000	[1]	97,000,000				0	[1]	0
New contracts		151,000,000	[1]	117,000,000				0	[1]	0				300,000,000	[1]	199,000,000
Matured, expired or settled contracts		(97,000,000)	[1]	(63,000,000)				(70,000,000)	[1]	(49,000,000)				(152,000,000)	[1]	(102,000,000)
Notional amounts at December 31		$ 132,000,000	[1]	£ 102,000,000				78,000,000	[1]	£ 48,000,000				148,000,000	[1]	£ 97,000,000
Weighted average forward rate at December 31 | £ / $		1.29		1.29	1.29	1.29	1.29
Active contracts at December 31		20		20	20	20	20
Forwards and Options [Member] | JPY
Derivative [Line Items]
Notional amounts at January 1		$ 144,000,000	[1]		¥ 15,500,000,000			109,000,000	[1]		12,840,000,000			0	[1]		0
New contracts		75,000,000	[1]		8,000,000,000			146,000,000	[1]		15,460,000,000			159,000,000	[1]		18,740,000,000
Matured, expired or settled contracts		(66,000,000)	[1]		(7,300,000,000)			(111,000,000)	[1]		(12,800,000,000)			(50,000,000)	[1]		(5,900,000,000)
Notional amounts at December 31		$ 153,000,000	[1]		¥ 16,200,000,000			144,000,000	[1]		¥ 15,500,000,000			109,000,000	[1]		¥ 12,840,000,000
Weighted average forward rate at December 31 | ¥ / $		106.25		106.25	106.25	106.25	106.25
Active contracts at December 31		34		34	34	34	34
Forwards and Options [Member] | USD [Member]
Derivative [Line Items]
Notional amounts at January 1 | $	[1]	$ 38,000,000						50,000,000						0
New contracts | $	[1]							15,000,000						71,000,000
Matured, expired or settled contracts | $	[1]							(27,000,000)						(21,000,000)
Notional amounts at December 31 | $	[1]							38,000,000						50,000,000
Forwards and Options [Member] | EUR
Derivative [Line Items]
Notional amounts at January 1		197,000,000	[1]				€ 174,000,000	310,000,000	[1]				275,000,000	354,000,000	[1]				284,000,000
New contracts		143,000,000	[1]				120,000,000	413,000,000	[1]				369,000,000	375,000,000	[1]				333,000,000
Matured, expired or settled contracts		(107,000,000)	[1]				(95,000,000)	(526,000,000)	[1]				(470,000,000)	(419,000,000)	[1]				(342,000,000)
Notional amounts at December 31		$ 233,000,000	[1]				€ 199,000,000	$ 197,000,000	[1]				€ 174,000,000	$ 310,000,000	[1]				€ 275,000,000
Weighted average forward rate at December 31 | € / $		1.17		1.17	1.17	1.17	1.17
Active contracts at December 31		29		29	29	29	29

[1] During 2017, 2016 and 2015, we exercised 44, 49 and 32 option contracts and realized gains of $12.6 million, $3.0 million and $14.6 million, respectively, in Foreign Currency and Derivative Gains (Losses), Net.