SHORT-TERM DEBT Credit Facility (Details) - USD ($) $ in Millions	Sep. 15, 2014	Jan. 31, 2018	Jul. 14, 2017	Jun. 09, 2015
Line of Credit Facility
Initiation date of credit facility	Sep. 15, 2014
Expiration date of credit facility	Sep. 15, 2019
Initial maximum borrowing capacity of credit facility	$ 400
Credit faciity terms (in years)	five
Credit facility limit increase			$ 300	$ 300
New maximum borrowing capacity of credit facility		$ 1,000
Amount outstanding on credit facility		$ 345