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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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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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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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	3 Months Ended			9 Months Ended		12 Months Ended
	Jan. 30, 2018	Jan. 31, 2017 $ / shares shares	Sep. 30, 2018 USD ($) $ / shares peer_group shares	Mar. 31, 2018 shares	Sep. 30, 2017 USD ($) $ / shares shares	Sep. 30, 2018 USD ($) program $ / shares peer_group shares	Sep. 30, 2017 USD ($) $ / shares shares	Dec. 31, 2017	Jun. 29, 2018 $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock shares reserved for future issuance (in shares)			11,000,000			11,000,000
Stock options exercised in period (in shares)			11,953		40,160	99,953	1,074,321
Net cash proceeds from the exercise of stock options \| $					$ 1	$ 2	$ 24
Share price (in dollars per share) \| $ / shares									$ 85.8
Stock options, exercisable (in shares)			289,033		300,000	289,033	300,000
Options exercisable, weighted average exercise price (in dollars per share) \| $ / shares			$ 36.55		$ 23.77	$ 36.55	$ 23.77
Total pre-tax intrinsic value of stock options exercised \| $			$ 1		$ 2	$ 6	$ 53
Compensation expense \| $			$ 18		$ 18	$ 51	$ 52
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%	15.00%
Common stock shares reserved for future issuance (in shares)			2,000,000			2,000,000
Maximum percentage of shares purchased from annual compensation						10.00%
Discount given to employees						15.00%
Compensation expense \| $			$ 1		$ 1	$ 3	$ 3
Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost \| $			58			$ 58
Weighted-average period unrecognized compensation cost is expected to be recognized, in years						1 year 10 months 15 days
PSUs \| One-Year Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost \| $			12			$ 12
Weighted-average period unrecognized compensation cost is expected to be recognized, in years						1 year 6 months
Performance period						1 year		1 year
Percentage of target amount granted, minimum						0.00%
Percentage of target amount granted, maximum						150.00%
Vesting period						3 years
Additional units granted above target (in shares)				14,497
PSUs \| Three-Year Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost \| $			$ 34			$ 34
Weighted-average period unrecognized compensation cost is expected to be recognized, in years						1 year 5 months 20 days
Performance period						3 years
Vesting period						3 years
Additional units granted above target (in shares)				237,876
Number of peer groups \| peer_group			2			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			$ 86.24		$ 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%