EQUITY AND EARNINGS PER SHARE - Outstanding Options by Recipient (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of unexercised options (in shares)	18,502,188
Options exercisable (in shares)	13,799,136
Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of unexercised options (in shares)	6,000	6,000
Stock Options | Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Date of grant/exercise	Various
Number of unexercised options (in shares)	6,000
Options exercisable (in shares)	6,000
Weighted average exercise price (in dollars per share)	$ 13.99
Intrinsic value of exercisable options	$ 0.0
Stock Options | Manager | 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Date of grant/exercise	2012
Number of unexercised options (in shares)	25,000
Options exercisable (in shares)	25,000
Weighted average exercise price (in dollars per share)	$ 7.19
Intrinsic value of exercisable options	$ 0.3
Stock Options | Manager | 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Date of grant/exercise	2013
Number of unexercised options (in shares)	835,571
Options exercisable (in shares)	835,571
Weighted average exercise price (in dollars per share)	$ 11.48
Intrinsic value of exercisable options	$ 5.3
Stock Options | Manager | 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Date of grant/exercise	2014
Number of unexercised options (in shares)	1,437,500
Options exercisable (in shares)	1,437,500
Weighted average exercise price (in dollars per share)	$ 12.20
Intrinsic value of exercisable options	$ 8.2
Stock Options | Manager | 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Date of grant/exercise	2015
Number of unexercised options (in shares)	8,543,539
Options exercisable (in shares)	8,543,539
Weighted average exercise price (in dollars per share)	$ 15.46
Intrinsic value of exercisable options	$ 20.7
Stock Options | Manager | 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Date of grant/exercise	2016
Number of unexercised options (in shares)	2,000,000
Options exercisable (in shares)	1,066,667
Weighted average exercise price (in dollars per share)	$ 14.20
Intrinsic value of exercisable options	$ 3.9
Stock Options | Manager | 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Date of grant/exercise	2017
Number of unexercised options (in shares)	5,654,578
Options exercisable (in shares)	1,884,859
Weighted average exercise price (in dollars per share)	$ 15.00
Intrinsic value of exercisable options	$ 5.4