STOCKHOLDERS’ EQUITY AND REDEEMABLE NONCONTROLLING INTEREST (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended													12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Mar. 31, 2021	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 30, 2020	Nov. 30, 2019	Jul. 01, 2015	May 04, 2006	May 03, 2006
Stockholders’ Equity and Redeemable Noncontrolling Interest [Line Items]
Preferred stock, par value		$ 1.00													$ 1.00
Preferred stock, shares outstanding		0													0
Common stock, par value		$ 0.01				$ 0.01									$ 0.01	$ 0.01					$ 0.01
Common stock, shares authorized		600,000,000				600,000,000									600,000,000	600,000,000					600,000,000	300,000,000
Dividends per common share		$ 0.53	$ 0.53	$ 0.53	$ 0.53	$ 0.53	$ 0.50	$ 0.50	$ 0.50	$ 0.45	$ 0.45	$ 0.45	$ 0.45
Additional authorized amount																			$ 1,000
Stock repurchase program, remaining authorized repurchase amount		$ 1,200													$ 1,200
Treasury stock value acquired cost method															$ 350	$ 325	$ 465
Reissuance of shares for employee benefit plan															2,000,000	3,000,000	2,000,000
Contributions from noncontrolling interest partners															$ 0	$ 16	$ 4
Redeemable noncontrolling interest		76				$ 77									76	77
UMass Joint Venture
Stockholders’ Equity and Redeemable Noncontrolling Interest [Line Items]
Ownership percentage by noncontrolling owners																				18.90%
Redeemable noncontrolling interest		$ 76				77									$ 76	$ 77
Treasury Stock, at Cost
Stockholders’ Equity and Redeemable Noncontrolling Interest [Line Items]
Purchases of treasury stock, shares															3,500,000	3,400,000	4,600,000
Treasury stock value acquired cost method															$ 350	$ 325	$ 465
Treasury Stock, at Cost | Accounts Payable and Accrued Liabilities
Stockholders’ Equity and Redeemable Noncontrolling Interest [Line Items]
Accrual						$ 3										$ 3
Forecast
Stockholders’ Equity and Redeemable Noncontrolling Interest [Line Items]
Dividends per common share	$ 0.56													$ 2.24
Subsequent Event
Stockholders’ Equity and Redeemable Noncontrolling Interest [Line Items]
Increase in quarterly dividends as percent																		5.70%
Maximum
Stockholders’ Equity and Redeemable Noncontrolling Interest [Line Items]
Preferred stock, shares authorized		10,000,000													10,000,000