EQUITY AND REDEEMABLE INTEREST (Common Stock) (Details) - USD ($)			3 Months Ended	9 Months Ended
	Jul. 01, 2020	Mar. 31, 2020	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Feb. 29, 2020	Dec. 31, 2019	Feb. 28, 2019
Class of Stock [Line Items]
Stock repurchased			$ 10,449,000
Proceeds from sale of shares		$ 383,800,000
Fees related to stock issuance		$ 700,000
Increase (Decrease) in Stockholders' Equity
Balance (in shares)				115,243,029
Issuance of stock (in shares)				135,054,384
Stock option exercises (in shares)				4,216,240
Vesting of restricted stock awards, net of shares withheld for tax (shares)				2,622,438
Balance (in shares)				258,446,513
AOG
Increase (Decrease) in Stockholders' Equity
Exchanges of AOG Units (in shares)				1,376,422
Redemptions of AOG Units (in shares)				(66,000)
Class A common stock
Class of Stock [Line Items]
Common stock, par value (in dollars per share)				$ 0.01			$ 0.01
Authorized amount						$ 150,000,000		$ 150,000,000
Stock repurchased (shares)					400,000
Stock repurchased					$ 10,400,000
Common stock, shares authorized (in shares)				1,500,000,000			1,500,000,000
Increase (Decrease) in Stockholders' Equity
Balance (in shares)				115,242,028
Issuance of stock (in shares)				19,854,764
Stock option exercises (in shares)				4,216,240
Vesting of restricted stock awards, net of shares withheld for tax (shares)				2,622,438
Balance (in shares)				143,826,710
Class A common stock | SSG Capital Holdings
Increase (Decrease) in Stockholders' Equity
Issuance of stock (in shares)	7,724,224
Class A common stock | AOG
Increase (Decrease) in Stockholders' Equity
Exchanges of AOG Units (in shares)				1,891,240
Redemptions of AOG Units (in shares)				0
Class A common stock | Underwritten
Class of Stock [Line Items]
Number of shares sold (in shares)		12,130,540
Class B common stock
Class of Stock [Line Items]
Common stock, par value (in dollars per share)				$ 0.01			$ 0.01
Common stock, shares authorized (in shares)				1,000			1,000
Increase (Decrease) in Stockholders' Equity
Balance (in shares)				1,000
Issuance of stock (in shares)				0
Stock option exercises (in shares)				0
Vesting of restricted stock awards, net of shares withheld for tax (shares)				0
Balance (in shares)				1,000
Class B common stock | AOG
Increase (Decrease) in Stockholders' Equity
Exchanges of AOG Units (in shares)				0
Redemptions of AOG Units (in shares)				0
Class C common stock
Class of Stock [Line Items]
Common stock, par value (in dollars per share)				$ 0.01			$ 0.01
Number of shares sold (in shares)				115,199,620
Common stock, shares authorized (in shares)				499,999,000
Increase (Decrease) in Stockholders' Equity
Balance (in shares)				1
Issuance of stock (in shares)				115,199,620
Stock option exercises (in shares)				0
Vesting of restricted stock awards, net of shares withheld for tax (shares)				0
Balance (in shares)				114,618,803
Class C common stock | AOG
Increase (Decrease) in Stockholders' Equity
Exchanges of AOG Units (in shares)				(514,818)
Redemptions of AOG Units (in shares)				(66,000)
Common Stock
Class of Stock [Line Items]
Common stock, shares authorized (in shares)				500,000,000			500,000,000