SHARE-BASED COMPENSATION - RSAs AND RSUs (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Risk-free rate of return (as a percent)	2.49%
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Maximum Performance Based RSU Target Performance Conditions Exceeded For Awards Granted during or after 2014	100.00%
Weighted average period over which unrecognized compensation cost will be recognized	2 years 10 days
Share-Based Compensation, Restricted Stock Awards And Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Stock price volatility	17.74%	17.46%	17.24%
Risk-free rate of return (as a percent)	2.46%	2.00%	1.49%
Share-Based Compensation, Performance Based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Nonvested, beginning of period (in shares)	1,242,169
Granted (in shares)	389,825
Vested (in shares)	(142,820)
Forfeited (in shares)	(402,193)
Nonvested, end of period (in shares)	1,086,981	1,242,169
Weighted average grant date fair value, beginning of period (in dollars per share)	$ 106.11
Weighted average grant date fair value, granted (in dollars per share)	113.54	$ 105.03	$ 110.54
Weighted average grant date fair value, vested (in dollars per share)	100.28
Weighted average grant date fair value, forfeited (in dollars per share)	103.34
Weighted average grant date fair value, end of period (in dollars per share)	$ 109.85	$ 106.11
Expected to vest (in shares)	1,066,375
Weighted average grant date fair value, expected to vest (in dollars per share)	$ 109.89
Share-Based Compensation, Service Based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Nonvested, beginning of period (in shares)	402,361
Granted (in shares)	260,594
Vested (in shares)	(209,395)
Forfeited (in shares)	(37,773)
Nonvested, end of period (in shares)	415,787	402,361
Weighted average grant date fair value, beginning of period (in dollars per share)	$ 105.01
Weighted average grant date fair value, granted (in dollars per share)	112.50	$ 107.60	$ 101.88
Weighted average grant date fair value, vested (in dollars per share)	102.68
Weighted average grant date fair value, forfeited (in dollars per share)	110.25
Weighted average grant date fair value, end of period (in dollars per share)	$ 119.96	$ 105.01
Expected to vest (in shares)	408,782
Weighted average grant date fair value, expected to vest (in dollars per share)	$ 109.65
Share-Based Compensation, Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Equity instruments other than options, vested in the period, fair value	$ 36	$ 32	$ 45
Nonvested awards, compensation cost not yet recognized	$ 32
Weighted average period over which unrecognized compensation cost will be recognized	2 years 25 days

Maximum Performance Based RSU Target Performance Conditions Exceeded For Awards Granted during or after 2014

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Share-based compensation arrangement by share-based payment award, equity instruments other than options, vested and expected to vest, outstanding, number.

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Share-based compensation arrangement by share-based payment award, equity instruments other than options, vested and expected to vest, weighted average grant date fair value.

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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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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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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The risk-free interest rate assumption that is used in valuing an option on its own shares.

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