Statement of Equity Statement - USD ($) $ in Millions	Total	Common Stock [Member]	Other Additional Capital [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]	Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]	Subsidiaries [Member]	Subsidiaries [Member] Common Stock [Member]	Subsidiaries [Member] Other Additional Capital [Member]	Subsidiaries [Member] AOCI Attributable to Parent [Member]	Subsidiaries [Member] Retained Earnings [Member]	Subsidiaries [Member] Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Shares, Issued		1						41,172,173
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ (584.3)	$ 0.0	$ 2,330.4	$ 0.8	$ (2,915.5)		$ 330.7	$ 0.4	$ 685.8	$ (36.2)	$ (319.3)
Other Comprehensive Income (Loss), Net of Tax				3.3			1.1			1.1
Net income	16.9				16.9		15.7
Net Income (Loss) Attributable to Parent											15.7
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	20.2						16.8
Stockholders' Equity, Other	0.0			(1.0)	1.0		(0.4)		(0.3)	(1.1)	1.0
Dividends, Common Stock, Cash							(23.8)		(23.8)
Proceeds from Contributions from Parent							80.0		(80.0)
Non-cash capital contribution	44.6		44.6
AOCI reclassed to Retained Earnings before tax | Adjustments for New Accounting Pronouncement [Member]	1.6						1.7
AOCI reclassed to Retained Earnings, net of tax | Adjustments for New Accounting Pronouncement [Member]	$ 1.0						$ 1.1
Common stock, par value (in USD per share)							$ 0.01
Common Stock, Shares Authorized	1,500						50,000,000
Shares, Issued		1						41,172,173
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ (519.5)	$ 0.0	2,375.0	3.1	(2,897.6)		$ 403.3	$ 0.4	741.7	(36.2)	(302.6)
Common stock, par value (in USD per share)							$ 0.01
Common Stock, Shares Authorized	1,500						50,000,000
Shares, Issued		1						41,172,173
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ (471.7)	$ 0.0	2,370.5	2.2	(2,844.4)		$ 445.3	$ 0.4	711.8	(35.3)	(231.6)
Other Comprehensive Income (Loss), Net of Tax	(0.4)			(0.4)		$ (0.5)	0.4			0.4		$ (0.3)
Net income	42.1						29.0
Net Income (Loss) Attributable to Parent					42.1						29.0
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	41.7						29.4
Stockholders' Equity, Other	0.1		0.1				(0.3)				(0.3)
Proceeds from Contributions from Parent							0.0
Non-cash capital contribution	$ 1.5		1.5
AOCI reclassed to Retained Earnings before tax | Adjustments for New Accounting Pronouncement [Member]							1.7
AOCI reclassed to Retained Earnings, net of tax | Adjustments for New Accounting Pronouncement [Member]							$ 1.1
Common stock, par value (in USD per share)							$ 0.01
Common Stock, Shares Authorized	1,500						50,000,000
Shares, Issued		1						41,172,173
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ (428.4)	$ 0.0	$ 2,372.1	$ 1.8	$ (2,802.3)		$ 474.4	$ 0.4	$ 711.8	$ (34.9)	$ (202.9)