NET INCOME PER SHARE (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Basic
Net income	$ 321.7	$ 245.2
Average shares outstanding (in shares)	91,075,973	91,952,828
Basic net income per share (in dollars per share)	$ 3.53	$ 2.67
Diluted
Net income	$ 321.7	$ 245.2
Average shares outstanding assuming dilution:
Average shares outstanding (in shares)	91,075,973	91,952,828
Stock options and other contingently issuable shares (in shares)	1,763,677	1,662,297
Non-vested restricted stock grants (in shares)	20,294	53,603
Average shares outstanding assuming dilution (in shares)	92,859,944	93,668,728
Diluted net income per share (in dollars per share)	$ 3.46	$ 2.62
Stock options and other contingently issuable shares with anti-dilutive effects (in shares)	471,638	49,501