Stock-Based Awards and Other Equity Instruments - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for new stock-based awards, shares	8,000
Stock-based compensation	$ 203	$ 149	$ 242
Market value of shares vested in period	68	65	57
Stock-based compensation tax benefit	39	38	56
Cash received from stock-based award exercises	149	213
Income tax benefit associated with employees exercise of stock-based awards	34	$ 100	$ 76
Unrecognized stock-based compensation expense	$ 450
Unrecognized stock-based compensation expense expected recognition period	2 years 5 months 19 days
Employee Stock Purchase Plan 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock purchase price as percentage of fair market value	85.00%
Eligible employees contribution of base compensation	10.00%
Employee stock purchase plan, shares purchased	170	141	139
Employee stock ownership plan, average purchase price of shares purchased	$ 101.26	$ 112.31	$ 95.63
Shares of our common stock reserved for issuance	1,000
Former Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation recovered due to forfeiture of awards		$ 41
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock price, as of year end (in dollars per share)	$ 112.65
Total intrinsic value of stock options exercised, value	$ 107	$ 249	$ 181
Stock options granted during the period	5,342	3,618	5,670
Vesting period	4 years
Weighted average exercise price of shares issued (in dollars per share)	$ 71.36	$ 62.67	$ 47.57
RSUs \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
RSUs \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
trivago
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Incremental stock based expense due to call of options previously exercised			$ 49

Current Income Tax Benefit Associated With Stock Based Awards.

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Incremental Stock Based Compensation Charge

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Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Aggregate number of common shares reserved for future issuance.

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Unrecognized cost of unvested share-based compensation awards.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

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Amount of cash inflow from exercise of stock options granted under share-based compensation arrangement.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The highest percentage of annual salary that an employee is permitted to utilize with respect to the plan.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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Net number of share options (or share units) granted during the period.

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The weighted average of per share prices paid for shares purchased on the open market for issuance to employees under the plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Purchase price of common stock expressed as a percentage of its fair value.

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Number of shares issued during the period as a result of an employee stock purchase plan.

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