QUARTERLY RESULTS OF OPERATIONS (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Apr. 30, 2019
Revenues	$ 1,461.0	$ 1,437.6	$ 1,348.5	$ 1,334.2	$ 1,464.5	$ 1,423.2	$ 1,397.2	$ 1,381.7	$ 5,581.3	$ 5,666.6	$ 5,474.7
Operating expenses	1,152.0	1,133.4	1,011.2	977.3	956.0	943.4	1,000.5	1,009.4	4,273.9	3,909.3	3,956.8
Operating income	309.0	304.2	337.3	356.9	508.5	479.8	396.7	372.3	1,307.4	1,757.3	1,517.9
Interest expense, net	141.6	140.0	143.5	143.9	144.7	136.8	133.6	127.2	569.0	542.3	455.4
Income from continuing operations before income taxes	167.4	164.2	193.8	213.0	363.8	343.0	263.1	245.1	738.4	1,215.0	1,062.5
Provision for income taxes	37.0	42.6	51.4	34.8	110.7	54.3	39.3	65.2	165.8	269.5	293.3
Income from continuing operations	130.4	121.6	142.4	178.2	253.1	288.7	223.8	179.9	572.6	945.5	769.2
(Loss) income from discontinued operations, net of taxes	(32.9)	(229.2)	(3.4)	(29.1)	31.8	7.8	(6.0)	(16.0)	(294.6)	17.6	19.5
Net income	$ 97.5	$ (107.6)	$ 139.0	$ 149.1	$ 284.9	$ 296.5	$ 217.8	$ 163.9	$ 278.0	$ 963.1	$ 788.7
Basic income (loss) per share (Note 4):
Income from continuing operations (in dollars per share)	$ 2.73	$ 2.47	$ 2.72	$ 3.36	$ 4.69	$ 5.27	$ 4.05	$ 3.25	$ 11.25	$ 17.24	$ 13.82
(Loss) income from discontinued operations (in dollars per share)	(0.70)	(4.69)	(0.07)	(0.55)	0.59	0.14	(0.11)	(0.29)	(5.89)	0.32	0.35
Net income (loss) per share (in dollars per share)	2.03	(2.22)	2.65	2.81	5.28	5.41	3.94	2.96	5.36	17.56	14.17
Diluted income (loss) per share (Note 4):
Income from continuing operations (in dollars per share)	2.74	2.41	2.71	3.35	4.67	5.25	4.04	3.23	11.24	17.17	13.75
(Loss) income from discontinued operations (in dollars per share)	(0.69)	(4.54)	(0.07)	(0.55)	0.58	0.14	(0.11)	(0.28)	(5.78)	0.32	0.35
Net income (loss) per share (in dollars per share)	$ 2.05	$ (2.13)	$ 2.64	$ 2.80	$ 5.25	$ 5.39	$ 3.93	$ 2.95	$ 5.46	$ 17.49	$ 14.10
Mandatory payment per credit agreement												$ 500.0
Long-term Debt	$ 2,849.9								$ 2,849.9
Epsilon
Diluted income (loss) per share (Note 4):
Mandatory payment per credit agreement	500.0			$ 500.0					500.0			$ 500.0
Epsilon | Senior Notes
Interest expense, net				5.6
Provision for income taxes				(1.7)
Diluted income (loss) per share (Note 4):
Long-term Debt	$ 1,900.0			$ 1,900.0					$ 1,900.0