SENIOR NOTES PAYABLE, Schedule of Senior Notes Payable (Details) - Senior Notes - USD ($)	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	May 31, 2017	Jul. 31, 2016	Mar. 31, 2012
Debt Instrument [Line Items]
Long-term debt, gross	$ 2,050,000,000		$ 1,550,000,000
Unaccreted premium/(discount)	10,000,000		11,000,000
Unamortized debt issuance costs	(15,000,000)		(11,000,000)
Total senior notes payable	2,045,000,000		1,550,000,000
5.625% senior notes, due 2024
Debt Instrument [Line Items]
Long-term debt, gross	250,000,000		250,000,000
Aggregate principal amount of the notes						$ 250,000,000
Interest rate (in hundredths)						5.625%
Percentage of principal amount of notes redeemed (in hundredths)						100.00%
Basis spread used in determining redemption price (in basis points)						0.50%
3.625% senior notes, due 2026
Debt Instrument [Line Items]
Long-term debt, gross	500,000,000		500,000,000
Aggregate principal amount of the notes					$ 500,000,000
Interest rate (in hundredths)					3.625%
Percentage of principal amount of notes redeemed (in hundredths)					100.00%
Basis spread used in determining redemption price (in basis points)					0.35%
4.65% senior notes, due 2030
Debt Instrument [Line Items]
Long-term debt, gross	500,000,000		0
Aggregate principal amount of the notes		$ 500,000,000
Interest rate (in hundredths)		4.65%
Percentage of principal amount of notes redeemed (in hundredths)		100.00%
Basis spread used in determining redemption price (in basis points)		0.50%
4.95% senior notes, due 2046
Debt Instrument [Line Items]
Long-term debt, gross	$ 800,000,000		$ 800,000,000
Aggregate principal amount of the notes				$ 300,000,000	$ 300,000,000
Interest rate (in hundredths)				4.95%	4.95%
Percentage of principal amount of notes redeemed (in hundredths)				100.00%
Basis spread used in determining redemption price (in basis points)				0.45%
4.95% senior notes, due 2046
Debt Instrument [Line Items]
Aggregate principal amount of the notes				$ 500,000,000