Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended									12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Selected Quarterly Financial Information [Abstract]
Revenue		$ 285.3	$ 312.4	$ 299.2	$ 288.9	$ 289.3	$ 299.8	$ 285.8	$ 292.9	$ 1,185.8	$ 1,167.8	$ 1,161.5
Operating Income (Loss)		10.5	25.5	27.4	29.6	25.0	36.2	29.7	37.1	93.0	128.0	176.9
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent		(1.6)	18.8	77.6	7.0	30.5	79.3	180.7	0.3	101.8	290.8	117.7
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent		0.3	0.0	0.0	0.0	2.1	1.0	10.9	48.9	0.3	62.9	(42.1)
Net income (loss)		$ (1.3)	$ 18.8	$ 77.6	$ 7.0	$ 32.6	$ 80.3	$ 191.6	$ 49.2	$ 102.1	$ 353.7	$ 75.6
Income (Loss) from Continuing Operations, Per Basic Share		$ (0.10)	$ 0.39	$ 1.79	$ 0.10	$ 0.66	$ 1.83	$ 4.25	$ (0.06)	$ 2.17	$ 6.69
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share		0.01	0.00	0.00	0.00	0.05	0.02	0.26	1.17	0.01	1.50
Earnings Per Share, Basic		(0.09)	0.39	1.79	0.10	0.71	1.85	4.51	1.11	2.18	8.19	$ 1.56
Income (Loss) from Continuing Operations, Per Diluted Share		(0.10)	0.38	1.78	0.10	0.66	1.83	4.15	(0.06)	2.17	6.68
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share		0.01	0.00	0.00	0.00	0.05	0.02	0.26	1.17	0.01	1.49
Earnings Per Share, Diluted		$ (0.09)	$ 0.38	$ 1.78	$ 0.10	$ 0.71	$ 1.85	$ 4.41	$ 1.11	$ 2.18	$ 8.17	$ 1.56
Restructuring and severance related charges (reversals)		$ 11.9					$ 0.3	$ 2.3	$ 3.4	$ 11.9	$ 6.0	$ (0.4)
Marketable Securities, Realized Gain (Loss)	$ 83.0	5.1	$ 33.3	$ 118.6		$ 36.3	117.7	295.2		157.0	449.2	192.8
Gains (Losses) on Extinguishment of Debt		$ (4.8)	$ (11.4)	$ (5.2)	$ (2.4)	$ (0.4)	$ (7.8)	(13.5)		19.0	20.9	19.6
Gain (Loss) on Disposition of Intangible Assets									$ 112.6	0.0	112.6	0.0
Gain on Liabilities and Other Assets transferred in Sale of Business Affiliate and Productive Assets								$ 15.9		$ 0.0	$ 15.9	$ 0.0