Employee Stock Compensation Plans - Allocated Compensation, Assumptions and Shares Available (Details) - USD ($) shares in Millions, $ 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]
Restricted Stock or Unit Expense	$ 65	$ 73	$ 61
Employee Stock Ownership Plan (ESOP), Compensation Expense	4	4	0
Stock or Unit Option Plan Expense	4	0	0
Total stock-based compensation (pre-tax)	73	77	61
Tax Benefit	(10)	(22)	(18)
Total stock-based compensation (net of tax)	$ 63	$ 55	$ 43
Stock Incentive Plan, 2006 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized (in shares)	22

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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-Section 50
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- Definition

The amount of expense, net of income tax, 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.

+ References

No definition available.

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- Definition

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

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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- Definition

The amount of plan compensation cost recognized during the period.

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- Definition

The noncash expense that represents the cost of restricted stock or unit distributed to employees as compensation.

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-Publisher FASB
-Name Accounting Standards Codification
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- Definition

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.

+ References

No definition available.

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- Definition

The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

+ References

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- Definition

The noncash expense that accounts for the value of stock or unit options distributed to employees as compensation.

+ References

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