EQUITY (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended									12 Months Ended
	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	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Dividends declared per share of stock		$ 0.46	$ 0.46	$ 0.46	$ 0.46	$ 0.42	$ 0.42	$ 0.42	$ 0.42	$ 1.84	$ 1.68	$ 1.40
Preferred Stock, Shares Authorized		50.0								50.0
Preferred Stock, Par or Stated Value Per Share		$ 0.01								$ 0.01
Common stock authorized and available for issuance		197.4								197.4
Stock Repurchase Program, Authorized Amount		$ 20								$ 20
Common Stock, Dividends, Declared, Annualized Basis										$ 1.68	$ 1.40	$ 1.20
Dividend Declared [Member]
Common Stock, Dividends, Per Share, Declared	$ 0.50
Common Stock, Dividends, Declared, Annualized Basis	$ 2.00