Stock-Based Compensation (Details 3) - Stock Option Plan - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stock option activity, shares
Stock options at the beginning of the period (in shares)	29,486
Stock options, granted (in shares)	4,133
Stock options, exercised (in shares)	(8,356)
Stock options, forfeited (in shares)	(928)
Stock options, expired (in shares)	(6)
Stock options at the ending of the period (in shares)	24,329	29,486
Stock options, vested and expected to vest (in shares)	23,448
Stock options, exercisable (in shares)	15,270
Weighted-average exercise price
Stock options, weighted-average strike price at the beginning of the period (in dollars per share)	$ 14.50
Stock options, weighted-average exercise price, granted (in dollars per share)	32.55
Stock options, weighted-average exercise price, exercised (in dollars per share)	13.08
Stock options, weighted-average exercise price, forfeited (in dollars per share)	18.44
Stock options, weighted-average exercise price, expired (in dollars per share)	8.73
Stock options, weighted-average strike price at the end of the period (in dollars per share)	17.90	$ 14.50
Stock options, weighted-average exercise price, vested and expected to vest (in dollars per share)	17.57
Stock options, weighted-average exercise price, exercisable (in dollars per share)	$ 13.51
Stock options, weighted-average remaining contractual term	5 years 11 months 22 days
Stock options, weighted-average remaining contractual term, vested and expected to vest	5 years 10 months 9 days
Stock options, weighted-average remaining contractual term, exercisable	4 years 2 months 8 days
Stock options, aggregate intrinsic value	$ 506
Stock options, aggregate intrinsic value, vested and expected to vest	496
Stock options, aggregate intrinsic value, exercisable	385
Stock options, intrinsic value of options exercised	125	$ 117	$ 104
Total grant date fair value of options vested	19	$ 19	$ 29
Stock-based compensation, unrecognized compensation	$ 43
Stock-based compensation, unrecognized compensation weighted-average period of recognition	1 year 6 months 10 days

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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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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Number of options or other stock instruments for which the right to exercise has lapsed under the terms of the plan agreements.

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of options outstanding, including both vested and non-vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of fully vested and expected to vest options that are exercisable.

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The number of exercisable share options (fully vested and expected to vest) that may be converted as of the balance sheet date.

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As of the balance sheet date, the weighted-average exercise price (at which grantees can acquire the shares reserved for issuance) for exercisable stock options that are fully vested or expected to vest.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of fully vested and expected to vest options outstanding.

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As of the balance sheet date, the number of shares into which fully vested and expected to vest stock options outstanding can be converted under the option plan.

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As of the balance sheet date, the weighted-average exercise price for outstanding stock options that are fully vested or expected to vest.

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

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options of the plan that expired.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average remaining contractual term for fully vested and expected to vest options that are exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average remaining contractual term for fully vested and expected to vest options outstanding, 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 options vested. Excludes equity instruments other than options, for example, but not limited to, share units, stock appreciation rights, restricted stock.

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Number of share options (or share units) exercised during the current period.

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