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Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Sep. 30, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	May 31, 2009
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant			2,400
Maximum contribution allowed under employee stock purchase plan as % of employee's earnings			15.00%
Total number of shares purchased under employee stock purchase plan			1,400
Plan period employee stock purchase plan, in months			3 months
Purchase price calculation for shares of stock under employee stock purchase plan			The purchase price for each share of stock is the lesser of 90% of the market price on the first day of the plan period or 100% of the market price on the last day of the plan period.
Incremental stock-based compensation cost due to acceleration of awards	$ 1	$ 4	$ 1	$ 4	$ 7
Total intrinsic value of options exercised in the period			44	76	53
Proceeds from stock plans			45	$ 91	$ 56
Intrinsic value of options outstanding			$ 86
Number of options exercisable			794	900	1,300
Weighted-average exercise price of exercisable options			$ 117.08	$ 103.63	$ 92.26
Weighted-average remaining contractual term of options exercisable			5 years 9 months 18 days
Number of options outstanding which are vested and expected to vest			1,800
Aggregate intrinsic value of outstanding options which are vested and expect to vest			$ 86
Weighted-average exercise price of outstanding options which are vested and expected to vest			$ 142.18
Weighted-average remaining contractual term of outstanding options which are vested and expected to vest			7 years 1 month 6 days
Unrecognized compensation costs on unvested options			$ 41
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			5 years
Stock-based compensation costs			$ 16	$ 17	$ 17
Weighted-average period of recognition for unrecognized compensation costs on nonvested awards			3 years 2 months 12 days
Shares granted			91
Weighted-average grant date fair value of shares granted			$ 207.85
Unvested shares at end of period			304	374
Unrecognized compensation costs on unvested awards			$ 32
Performance Stock Unit Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation costs			$ 5
Weighted-average period of recognition for unrecognized compensation costs on nonvested awards			2 years 3 months 18 days
Shares granted			40	40	27
Weighted-average grant date fair value of shares granted			$ 235.63
Unvested shares at end of period			100	64
Unrecognized compensation costs on unvested awards			$ 14
Stock-based compensation costs, less than $1 million				Less than $1 million
Performance Stock Unit Plan [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights			0.00%
Performance Stock Unit Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights			200.00%
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation costs			$ 1	$ 1	$ 1
Shares granted			5	8	10
Weighted-average grant date fair value of shares granted			$ 194.73	$ 130.35	$ 113.88
Unvested shares at end of period			5
Employee Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation costs			$ 1	$ 1	$ 1
Employee Stock [Member] | Employee Stock Purchase Plan Of 2009 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized under plan						900
Equity Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			5 years
Award expiration period			10 years
Weighted-average period of recognition for unrecognized compensation costs on nonvested awards			3 years 6 months

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