Statement of Shareholders' Equity (Statement) - USD ($) $ in Millions	Total	Subsidiaries [Member]	Common Stock [Member]	Common Stock [Member] Subsidiaries [Member]	Other Additional Capital [Member]	Other Additional Capital [Member] Subsidiaries [Member]	AOCI Attributable to Parent [Member]	AOCI Attributable to Parent [Member] Subsidiaries [Member]	Retained Earnings [Member]	Retained Earnings [Member] Subsidiaries [Member]
Shares, Issued			1	41,172,173
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ (121.4)	$ 782.2	$ 0.0	$ 0.4	$ 2,601.3	$ 822.5	$ (4.8)	$ (31.8)	$ (2,717.9)	$ (8.9)
Other Comprehensive Income (Loss), Net of Tax	0.1	0.7
Net income	15.4	16.9
Stockholders' Equity, Other		(0.3)				0.0		0.0		0.3
Payments of Dividends		9.0				9.0				0.0
Net Income (Loss) Attributable to Parent	15.4	16.9
Other Comprehensive Income (Loss), Net of Tax	0.2	2.0
Net income	(4.1)	14.1
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	(3.9)	16.1
Payments of Dividends		49.0				15.0				34.0
Proceeds from Contributions from Parent	0.0	0.0
Shares, Issued			1	41,172,173
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(105.9)	790.5	$ 0.0	$ 0.4	2,601.3	813.5	(4.7)	(31.1)	(2,702.5)	7.7
Other Comprehensive Income (Loss), Net of Tax	0.0	0.7
Net income	0.2	7.3
Payments of Dividends		25.0				10.0				15.0
Net Income (Loss) Attributable to Parent	0.2	7.3
Shares, Issued			1	41,172,173
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(105.7)	773.5	$ 0.0	$ 0.4	2,601.3	803.5	(4.7)	(30.4)	(2,702.3)	0.0
Other Comprehensive Income (Loss), Net of Tax	0.1	0.6
Net income	(19.7)	(10.1)
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	(19.6)	(9.5)
Stockholders' Equity, Other		0.0				(0.1)				0.1
Payments of Dividends		15.0				15.0
Net Income (Loss) Attributable to Parent	(19.7)	(10.1)
Shares, Issued			1	41,172,173
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(125.3)	749.0	$ 0.0	$ 0.4	2,601.3	788.6	(4.6)	(29.8)	(2,722.0)	(10.2)
Shares, Issued			1	41,172,173
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ (123.7)	$ 741.8	$ 0.0		2,601.3		(2.4)		(2,722.6)
Common Stock, Shares Authorized	1,500	50,000,000
Common Stock, Value, Issued	$ 0.0	$ 0.4
Other paid-in capital	2,601.3	773.6
Accumulated other comprehensive income	(2.4)	(26.8)
Retained Earnings (Accumulated Deficit)	(2,722.6)	$ (5.4)
Par value common shares (in USD per share)		$ 0.01
Other Comprehensive Income (Loss), Net of Tax	(0.2)	$ 0.1						0.1
Net income	1.2									9.6
Stockholders' Equity, Other		0.1								0.1
Payments of Dividends		15.0				13.1				1.9
Net Income (Loss) Attributable to Parent	1.2	9.6
Other Comprehensive Income (Loss), Net of Tax	(0.5)	0.3
Net income	34.6	52.8
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	34.1	53.1
Payments of Dividends		65.0				8.7				56.3
Proceeds from Contributions from Parent	239.0	260.0
Shares, Issued			1	41,172,173
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(122.7)	736.6	$ 0.0	$ 0.4	2,601.3	760.5	(2.6)	(26.7)	(2,721.4)	2.4
Other Comprehensive Income (Loss), Net of Tax	(0.1)	0.1						0.1
Net income	(5.2)									(0.4)
Stockholders' Equity, Other	0.1	0.1			0.1	0.1				0.0
Payments of Dividends		40.0				37.8				2.2
Net Income (Loss) Attributable to Parent	(5.2)	(0.4)
Proceeds from Contributions from Parent	112.0	125.0			112.0
Shares, Issued			1	41,172,173
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(15.9)	821.4	$ 0.0	$ 0.4	2,713.4	847.8	(2.7)	(26.6)	(2,726.6)	(0.2)
Other Comprehensive Income (Loss), Net of Tax	(0.2)	0.1						0.1
Net income	38.6	43.6
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	38.4	43.7
Stockholders' Equity, Other		(0.1)				0.0				(0.1)
Payments of Dividends		10.0				5.4				4.6
Net Income (Loss) Attributable to Parent	38.6	43.6
Proceeds from Contributions from Parent	127.0	135.0			127.0
Shares, Issued			1	41,172,173
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 149.5	$ 990.0	$ 0.0	$ 0.4	$ 2,840.4	$ 977.4	$ (2.9)	$ (26.5)	$ (2,688.0)	$ 38.7
Common Stock, Shares Authorized	1,500	50,000,000
Common Stock, Value, Issued	$ 0.0	$ 0.4
Other paid-in capital	2,840.4	977.4
Accumulated other comprehensive income	(2.9)	(26.5)
Retained Earnings (Accumulated Deficit)	$ (2,688.0)	$ 38.7
Par value common shares (in USD per share)		$ 0.01