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]
Shares, Issued		1						41,172,173
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning Balance at Dec. 31, 2019	$ (371.9)	$ 0.0	$ 2,370.7	$ (3.6)	$ (2,739.0)		$ 473.4	$ 0.4	$ 617.0	$ (36.9)	$ (107.1)
Other Comprehensive Income (Loss), Net of Tax	(0.3)						0.4
Net income/ (loss)	1.9
Net Income (Loss) Attributable to Parent							11.7
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	1.6						12.1
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance at Mar. 31, 2020	(370.3)	0.0	2,370.7	(3.9)	(2,737.1)		485.5		617.0	(36.5)	(95.4)
Dividends, Common Stock, Cash							(14.2)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning Balance at Dec. 31, 2019	(371.9)	0.0	2,370.7	(3.6)	(2,739.0)		473.4	0.4	617.0	(36.9)	(107.1)
Other Comprehensive Income (Loss), Net of Tax	(0.1)						1.3
Net income/ (loss)	5.4						29.5
Proceeds from Contributions from Parent	(98.0)						(150.0)
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	5.3						30.8
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance at Jun. 30, 2020	(268.6)	$ 0.0	2,468.7	(3.7)	(2,733.6)		640.1	$ 0.4	752.9	(35.6)	(77.6)
Shares, Issued		1						41,172,173
Dividends, Common Stock, Cash							(14.2)		(14.2)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning Balance at Mar. 31, 2020	(370.3)	$ 0.0	2,370.7	(3.9)	(2,737.1)		485.5		617.0	(36.5)	(95.4)
Other Comprehensive Income (Loss), Net of Tax	0.2			0.2			0.9
Net income/ (loss)	3.5						17.8
Net Income (Loss) Attributable to Parent					3.5		17.8
Proceeds from Contributions from Parent							(150.0)		(150.0)
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	3.7						18.7
Non-cash capital contribution	98.0		98.0
Stockholders' Equity, Other							(0.1)		(0.1)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance at Jun. 30, 2020	$ (268.6)	$ 0.0	2,468.7	(3.7)	(2,733.6)		$ 640.1	$ 0.4	752.9	(35.6)	(77.6)
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
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
Common Stock, Value, Issued	$ 0.0
Additional Paid in Capital, Common Stock	2,468.8
Accumulated Other Comprehensive Income (Loss), Net of Tax	(12.3)					$ 13.6	$ (42.1)
Retained Earnings (Accumulated Deficit)	(2,740.0)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning Balance at Dec. 31, 2020	(283.5)	$ 0.0	2,468.8	(12.3)	(2,740.0)		616.7	$ 0.4	714.4	(42.1)	(56.0)
Other Comprehensive Income (Loss), Net of Tax	0.3									1.0
Net income/ (loss)	13.6
Net Income (Loss) Attributable to Parent											18.3
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	13.9						19.3
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance at Mar. 31, 2021	(269.6)	0.0	2,468.8	(12.0)	(2,726.4)		636.0	0.4	714.4	(41.1)	(37.7)
Dividends, Common Stock, Cash									(7.0)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning Balance at Dec. 31, 2020	(283.5)	0.0	2,468.8	(12.3)	(2,740.0)		616.7	0.4	714.4	(42.1)	(56.0)
Other Comprehensive Income (Loss), Net of Tax	0.6					(0.4)	1.9
Net income/ (loss)	14.0						26.9
Proceeds from Contributions from Parent	0.0						0.0
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	14.6						28.8
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance at Jun. 30, 2021	(268.9)	$ 0.0	2,468.8	(11.7)	(2,726.0)		638.5	$ 0.4	707.4	(40.2)	(29.1)
Shares, Issued		1						41,172,173
Dividends, Common Stock, Cash							(7.0)		(7.0)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning Balance at Mar. 31, 2021	(269.6)	$ 0.0	2,468.8	(12.0)	(2,726.4)		636.0	$ 0.4	714.4	(41.1)	(37.7)
Other Comprehensive Income (Loss), Net of Tax	0.3						0.9			0.9
Net income/ (loss)	0.4						8.6
Net Income (Loss) Attributable to Parent					0.4						8.6
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	0.7						9.5
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance at Jun. 30, 2021	$ (268.9)	$ 0.0	$ 2,468.8	$ (11.7)	$ (2,726.0)		$ 638.5	$ 0.4	$ 707.4	$ (40.2)	$ (29.1)
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
Common Stock, Value, Issued	$ 0.0						$ 0.4
Additional Paid in Capital, Common Stock	2,468.8						707.4
Accumulated Other Comprehensive Income (Loss), Net of Tax	(11.7)					$ 13.2	(40.2)
Retained Earnings (Accumulated Deficit)	$ (2,726.0)						$ (29.1)