CAPITAL STOCK - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended
	Jan. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jun. 30, 2019	Dec. 31, 2018	Sep. 07, 2018
Class of Stock [Line Items]
Authorized amount of stock available for repurchase						$ 1,500,000,000
Shares repurchased (in shares)		18,300,000		18,300,000
Aggregate amount of repurchased shares		$ 155,000,000.0		$ 155,000,000
Options exercised under incentive plans (in shares)			0
Preferred Stock, par value (in dollars per share)		$ 0.01		$ 0.01			$ 0.01
Preferred stock, redemption price (in dollars per share)		$ 25.00		$ 25.00
Preferred stock, shares issued (in shares)		81,900,000		81,900,000			73,400,000
7.625% Series C Cumulative Redeemable Preferred Stock
Class of Stock [Line Items]
Preferred stock, redemption price (in dollars per share)		$ 25.00		$ 25.00
Preferred stock redeemed (in shares)				7,000,000.0	5,000,000.0
Preferred stock dividend rate, percentage				7.625%
Redemption of preferred stock				$ 175,000,000.0	$ 125,000,000.0
Preferred stock, shares issued (in shares)		0		0			7,000,000
Series H Preferred Stock
Class of Stock [Line Items]
Preferred stock, redemption price (in dollars per share)		$ 25.00		$ 25.00
Preferred stock redeemed (in shares)				2,200,000
Preferred stock dividend rate, percentage				8.125%
Redemption of preferred stock				$ 55,000,000.0
Preferred stock, shares issued (in shares)		0	2,200,000	0	2,200,000		2,200,000
Series I
Class of Stock [Line Items]
Preferred stock dividend rate, percentage				6.75%
Preferred stock, shares issued (in shares)		17,700,000		17,700,000			0
Proceeds from issuance of redeemable preferred stock				$ 442,500,000
6.50% Series G Cumulative Redeemable Preferred Stock
Class of Stock [Line Items]
Preferred stock dividend rate, percentage				6.50%	6.50%
Preferred stock, shares issued (in shares)		17,000,000	17,000,000.0	17,000,000	17,000,000.0		17,000,000
Proceeds from issuance of redeemable preferred stock					$ 425,000,000.0
7.625% Series E Cumulative Redeemable Preferred Stock
Class of Stock [Line Items]
Preferred stock redeemed (in shares)					11,500,000
Preferred stock dividend rate, percentage					7.625%
Redemption of preferred stock					$ 287,500,000
Public Offering
Class of Stock [Line Items]
Sale of stock, shares issued (in shares)			75,000,000.0	75,000,000.0	75,000,000.0
Proceeds from sale of stock			$ 753,800,000	$ 730,500,000	$ 753,800,000
Option granted to underwriters to purchase additional shares			30 days		30 days
Public Offering, Additional Share Purchase Option
Class of Stock [Line Items]
Sale of stock, shares issued (in shares)			11,300,000	11,300,000	11,300,000.0
Proceeds from sale of stock			$ 113,100,000	$ 109,600,000	$ 113,100,000
Option granted to underwriters to purchase additional shares				30 days
At-the-market Sale Program
Class of Stock [Line Items]
Sale of stock, shares issued (in shares)				56,000,000.0	24,000,000.0
Proceeds from sale of stock				$ 569,100,000	$ 251,100,000
Aggregate stock offering price	$ 1,500,000,000
Mountain Merger Sub Corporation | Series H Preferred Stock
Class of Stock [Line Items]
Preferred Stock, par value (in dollars per share)								$ 0.01