SHAREHOLDERS' EQUITY - Stock Repurchase (Details) - USD ($) shares in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Sep. 17, 2019
Class of Stock [Line Items]
Stock repurchase program, authorized amount						$ 2,000,000,000.0
Repurchase and retirement of common stock (in shares)			20.1	18.6	9.2
Repurchase and retirement of common stock to offset the dilutive impact of the grant of long-term stock awards (in shares)			0.6	0.7	0.9
Remaining authorized repurchase amount		$ 1,500,000,000	$ 1,500,000,000
Repurchase and retirement of common stock			$ 896,000,000	$ 654,000,000	$ 331,000,000
Common Stock [Member]
Class of Stock [Line Items]
Stock repurchased during period, value		$ 400,000,000
Stock repurchased during period, shares (in shares)		7.3
Subsequent Event [Member] | Common Stock [Member]
Class of Stock [Line Items]
Stock repurchased during period, additional shares (in shares)	1.2