Consolidated Statements of Shareowners' Deficit - USD ($) shares in Millions, $ in Millions		3 Months Ended				12 Months Ended
		Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			$ (121.7)		$ (298.2)	$ (121.7)	$ (298.2)	$ (648.5)
Net income		$ (16.2)	$ 60.4	$ (1.3)	$ 7.0	35.1	102.1	353.7
Reclassification adjustment to accumulated deficit for stranded other comprehensive income taxes arising from tax reform (a)						0.0
Other comprehensive income (loss)						(51.2)	80.7	2.9
Shares issued under employee plans						0.5	3.6	0.1
Shares purchased under employee plans and other						(1.3)	0.2	(0.1)
Stock-based compensation						$ 5.9	$ 5.1	$ 4.1
Repurchase and retirement of shares						0.0	(0.2)	0.0
Repurchase and retirement of shares							$ (4.8)
Dividends on preferred stock						$ (10.4)	(10.4)	$ (10.4)
Ending Balance		$ (143.1)		$ (121.7)		$ (143.1)	$ (121.7)	$ (298.2)
Preferred Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance			3.1		3.1	3.1	3.1	3.1
Beginning Balance			$ 129.4		$ 129.4	$ 129.4	$ 129.4	$ 129.4
Balance		3.1		3.1		3.1	3.1	3.1
Ending Balance		$ 129.4		$ 129.4		$ 129.4	$ 129.4	$ 129.4
Common Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance			42.1		42.0	42.1	42.0	41.9
Beginning Balance			$ 0.4		$ 0.4	$ 0.4	$ 0.4	$ 0.4
Shares issued under employee plans						0.1	0.3	0.1
Shares issued under employee plans						$ 0.0	$ 0.0	$ 0.0
Repurchase and retirement of shares							(0.2)
Repurchase and retirement of shares							$ 0.0
Balance		42.2		42.1		42.2	42.1	42.0
Ending Balance		$ 0.4		$ 0.4		$ 0.4	$ 0.4	$ 0.4
Additional Paid-in Capital [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			2,570.9		2,577.7	2,570.9	2,577.7	2,584.6
Shares issued under employee plans						0.5	3.6	0.1
Shares purchased under employee plans and other						(1.3)	(0.3)	(0.7)
Stock-based compensation						5.9	5.1	4.1
Repurchase and retirement of shares							(4.8)
Dividends on preferred stock						(10.4)	(10.4)	(10.4)
Ending Balance		2,565.6		2,570.9		2,565.6	2,570.9	2,577.7
Retained Earnings [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			(2,732.1)		(2,834.2)	(2,732.1)	(2,834.2)	(3,187.9)
Net income						35.1	102.1	353.7
Reclassification adjustment to accumulated deficit for stranded other comprehensive income taxes arising from tax reform (a)	[1]					32.2
Ending Balance		(2,664.8)		(2,732.1)		(2,664.8)	(2,732.1)	(2,834.2)
AOCI Attributable to Parent
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			$ (90.3)		$ (171.0)	(90.3)	(171.0)	(173.9)
Reclassification adjustment to accumulated deficit for stranded other comprehensive income taxes arising from tax reform (a)	[1]					(32.2)
Other comprehensive income (loss)						(51.2)	80.7	2.9
Ending Balance		$ (173.7)		$ (90.3)		$ (173.7)	$ (90.3)	$ (171.0)
Treasury Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance			0.0		(0.1)	0.0	(0.1)	(0.1)
Beginning Balance			$ 0.0		$ (0.5)	$ 0.0	$ (0.5)	$ (1.1)
Shares purchased under employee plans and other							0.1	0.0
Shares purchased under employee plans and other							$ 0.5	$ 0.6
Balance		0.0		0.0		0.0	0.0	(0.1)
Ending Balance		$ 0.0		$ 0.0		$ 0.0	$ 0.0	$ (0.5)

[1] Per ASU 2018-02, entities can elect to make a one-time reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from newly enacted corporate tax rates under the Tax Cuts and Jobs Act. The Company recorded a provisional amount in 2017.