PREFERRED STOCK - Additional Information (Detail) $ / shares in Units, $ in Millions			1 Months Ended			12 Months Ended
	Sep. 14, 2018 shares	Sep. 15, 2015 USD ($) $ / shares shares	Aug. 31, 2018 shares	May 31, 2018 shares	Feb. 28, 2018 shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($)
Class of Stock [Line Items]
Preferred stock, authorized (in shares)						1,000,000	1,000,000
Preferred stock, issued (in shares)	638,190					0	673,380
Preferred stock, outstanding (in shares)						0	673,380
Depositary shares (in shares)		7,700,000
Preferred stock, dividend rate		5.25%
Preferred stock, par value (in dollars per share) | $ / shares		$ 0.01				$ 0.01	$ 0.01
Gross proceeds from issuance of preferred stock | $		$ 770.0
Conversion of preferred stock to common stock conversion ratio	7.3394
Conversion of preferred stock to common stock, (in shares)	4,700,000
Preferred stock, liquidation preference (in dollars per share) | $ / shares		$ 1,000
Depositary Shares, Liquidation Preference Per Share | $ / shares		100.00
Dividends paid on mandatory convertible preferred shareholders | $						$ 25.5	$ 36.3	$ 39.4
Increase to retained earnings on repurchase of depository shares | $						$ 16.9	$ 17.3	$ 11.3
Depositary shares repurchased during period (in shares)			50,000	150,000	151,900	351,900
Depository shares equivalent to preferred stock units (in shares)						35,190
Preferred Stock
Class of Stock [Line Items]
Issuance of preferred stock (in dollars per share) | $ / shares		$ 100.00
Conversion of preferred stock to common stock, (in shares)						(600,000)