CAPITAL STOCK - Schedule of Preferred Stock (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Class of Stock [Line Items]
Shares Authorized (in shares)	85,150,000	85,150,000
Shares Issued (in shares)	81,900,000	81,900,000
Shares Outstanding (in shares)	81,900,000	81,900,000
Carrying Value	$ 1,982,026	$ 1,982,026	[1]
Series C
Class of Stock [Line Items]
Shares Outstanding (in shares)	0	0
Series D
Class of Stock [Line Items]
Shares Authorized (in shares)	18,400,000	18,400,000
Shares Issued (in shares)	18,400,000	18,400,000
Shares Outstanding (in shares)	18,400,000	18,400,000
Carrying Value	$ 445,457	$ 445,457
Contractual Rate	7.50%
Series H
Class of Stock [Line Items]
Shares Outstanding (in shares)	0	0
Series F
Class of Stock [Line Items]
Shares Authorized (in shares)	28,800,000	28,800,000
Shares Issued (in shares)	28,800,000	28,800,000
Shares Outstanding (in shares)	28,800,000	28,800,000
Carrying Value	$ 696,910	$ 696,910
Contractual Rate	6.95%
Floating annual rate	4.993%
Series G
Class of Stock [Line Items]
Shares Authorized (in shares)	19,550,000	19,550,000
Shares Issued (in shares)	17,000,000	17,000,000
Shares Outstanding (in shares)	17,000,000	17,000,000
Carrying Value	$ 411,335	$ 411,335
Contractual Rate	6.50%
Floating annual rate	4.172%
Series I
Class of Stock [Line Items]
Shares Authorized (in shares)	18,400,000	18,400,000
Shares Issued (in shares)	17,700,000	17,700,000
Shares Outstanding (in shares)	17,700,000	17,700,000
Carrying Value	$ 428,324	$ 428,324
Contractual Rate	6.75%
Floating annual rate	4.989%

[1] Derived from the audited consolidated financial statements at December 31, 2019.