PREFERRED STOCK - Additional Information (Detail) $ in Millions		1 Months Ended			3 Months Ended		9 Months Ended
	Sep. 14, 2018 shares	Aug. 31, 2018 shares	May 31, 2018 shares	Feb. 28, 2018 shares	Sep. 30, 2018 USD ($) shares	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) shares	Sep. 30, 2017 USD ($)	Dec. 31, 2017 shares
Equity [Abstract]
Preferred stock, authorized (in shares)					1,000,000		1,000,000		1,000,000
Preferred stock, issued (in shares)	638,190				0		0		700,000
Preferred stock, outstanding (in shares)					0		0		700,000
Dividends paid on mandatory convertible preferred shareholders | $					$ 8.4	$ 8.9	$ 25.5	$ 27.5
Increase to retained earnings on repurchase of mandatory convertible preferred stock | $					$ 2.4	$ 5.4	$ 16.9	$ 14.4
Depositary shares purchased during period (in shares)		50,000	150,000	151,900			351,900
Depository shares equivalent to preferred stock units (in shares)					35,190		35,190
Conversion of preferred stock to common stock conversion ratio	7.3394
Conversion of preferred stock to common stock, (in shares)	4,700,000