Maximum Percentage of Shares Purchased from Annual Compensation.

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Number of peer groups.

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Number of Performance-Based Programs

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Percentage Of Target Amount Granted Maximum

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Percentage Of Target Amount Granted Minimum

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Performance Based Long Term Incentive Program Weighted Percentage

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Rate of Discount given to Employees.

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- Definition

Share Based Compensation Arrangement By Share Based Payment Award Percentage Of Shares Earned Maximum

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Share Based Compensation Arrangement By Share Based Payment Award Percentage Of Shares Earned Minimum

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Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Grants in Period

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Share-based Compensation Arrangement by Share-based Payment Award, Performance Period

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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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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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Discount rate from fair value on purchase date that participants pay for shares.

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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 number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option 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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Gross number of share options (or share units) granted during the period.

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Price of a single share of a number of saleable stocks of a company.

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Percentage of vesting of share-based compensation awards.

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Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average grant-date fair value of options vested.

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

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Share-Based Compensation (Narrative) (Details) $ / shares in Units, $ in Millions		1 Months Ended	2 Months Ended	3 Months Ended	12 Months Ended
	Jan. 30, 2018	Jan. 31, 2017 $ / shares shares	Feb. 22, 2019 shares	Dec. 31, 2017 $ / shares shares	Dec. 31, 2018 USD ($) program $ / shares peer_group shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock shares reserved for future issuance (in shares)					11,000,000
Stock option awards granted (in shares)						268,817
Stock options exercised in period (in shares)					118,094	1,102,830	1,219,820
Net cash proceeds from the exercise of stock options \| $					$ 3	$ 24	$ 41
Share price (in dollars per share) \| $ / shares					$ 81.57
Stock options, exercisable (in shares)				300,000	268,504	300,000
Options exercisable, weighted average exercise price (in dollars per share) \| $ / shares				$ 23.55	$ 37.51	$ 23.55
Total pre-tax intrinsic value of stock options exercised \| $					$ 7	$ 54	$ 40
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Discount from market price				15.00%	15.00%	15.00%
Common stock shares reserved for future issuance (in shares)					1,900,000
Maximum percentage of shares purchased from annual compensation					10.00%
Discount given to employees					15.00%
Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost \| $					$ 55
Weighted-average period unrecognized compensation cost is expected to be recognized, in years					1 year 9 months 1 day
PSUs \| One-Year Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost \| $					$ 14
Weighted-average period unrecognized compensation cost is expected to be recognized, in years					1 year 7 months 1 day
Performance period					1 year
Percentage of target amount granted, minimum					0.00%
Percentage of target amount granted, maximum					150.00%
Vesting period					3 years
PSUs \| Three-Year Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost \| $					$ 28
Weighted-average period unrecognized compensation cost is expected to be recognized, in years					1 year 5 months 2 days
Performance period					3 years
Vesting period					3 years
Number of peer groups \| peer_group					2
Performance-based long-term incentive program weighted percentage					50.00%
Minimum payout					0.00%
Maximum payout					200.00%
Share price (in dollars per share) \| $ / shares				$ 69.45	$ 86.24	$ 69.45
PSUs \| Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of performance-based programs \| program					2
PSUs, Negative TSR \| Three-Year Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum payout					100.00%
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option awards granted (in shares)					0
Weighted-average grant date fair value (in dollars per share) \| $ / shares		$ 66.68
Expected life (in years)		6 years
Employee Stock Option \| CEO
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		3 years
Stock option awards granted (in shares)		268,817
Second Anniversary \| Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage					25.00%
Second Anniversary \| Employee Stock Option \| CEO
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	33.33%
Third Anniversary \| Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage					25.00%
Fourth Anniversary \| Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage					50.00%
Subsequent Event \| PSUs \| One-Year Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional units granted above target (in shares)			51,914
Subsequent Event \| PSUs \| Three-Year Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional units granted above target (in shares)			99,622