Supplemental Unaudited Quarterly Financial Information Consolidated Statements of Changes in Stockholders' Equity (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Jun. 30, 2014	Jun. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	$ 388.4	$ 390.5	$ 364.8	$ 381.4	$ 254.0	$ 257.4	$ 255.5	$ 293.5	$ 381.4	$ 293.5	$ 381.4	$ 293.5	$ 381.4	$ 293.5	$ 425.0
Other comprehensive income (loss)		(6.9)	29.7	(1.4)		10.8	(2.6)	(12.5)	28.3	(15.1)	21.4	(4.3)	16.7	(21.5)	7.6
Net income (loss)	(94.9)	4.8	(4.0)	(15.2)	99.6	(14.2)	4.5	(25.5)	(19.2)	(21.0)	(14.4)	(35.2)	(109.3)	64.4	(139.1)
Change in stockholder’s equity				(16.6)				(38.0)	9.1	(36.1)	7.0	(39.5)	(77.6)	87.9	(131.5)
Balance, end of period	303.8	388.4	390.5	364.8	381.4	254.0	257.4	255.5	390.5	257.4	388.4	254.0	303.8	381.4	293.5
COMMON STOCK:
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period																2.5
Balance, end of period	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5
ADDITIONAL PAID-IN CAPITAL:
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period																802.2
Balance, end of period	862.2	847.2	847.2	847.2	847.2	802.2	802.2	802.2	847.2	802.2	847.2	802.2	862.2	847.2	802.2	802.2
ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS):
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period				(12.7)				8.8	(12.7)	8.8	(12.7)	8.8	(12.7)	8.8	1.2
Other comprehensive income (loss)				(1.4)				(12.5)	28.3	(15.1)	21.4	(4.3)	16.7	(21.5)	7.6
Balance, end of period	4.0	8.7	15.6	(14.1)	(12.7)	4.5	(6.3)	(3.7)	15.6	(6.3)	8.7	4.5	4.0	(12.7)	8.8
RETAINED EARNINGS (ACCUMULATED DEFICIT):
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period				(455.6)				(520.0)	(455.6)	(520.0)	(455.6)	(520.0)	(455.6)	(520.0)	(380.9)
Net income (loss)				(15.2)				(25.5)	(19.2)	(21.0)	(14.4)	(35.2)	(109.3)	64.4	(139.1)
Balance, end of period	(564.9)	(470.0)	(474.8)	(470.8)	(455.6)	(555.2)	(541.0)	(545.5)	(474.8)	(541.0)	(470.0)	(555.2)	(564.9)	(455.6)	(520.0)
As reported
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period		387.9	352.8	372.5		263.3	258.7	295.1	372.5	295.1	372.5	295.1	372.5	295.1	424.0
Other comprehensive income (loss)		(8.7)	32.3	(2.9)		10.2	0	(16.0)	29.4	(16.0)	20.7	(5.8)		(23.3)	8.8
Net income (loss)				(16.8)				(20.4)	(14.0)	(15.8)	(10.7)	(31.0)		55.7	(137.7)
Change in stockholder’s equity				(19.7)				(36.4)	15.4	(31.8)	10.0	(36.8)		77.4	(128.9)
Balance, end of period		382.5	387.9	352.8	372.5	258.3	263.3	258.7	387.9	263.3	382.5	258.3		372.5	295.1
As reported | COMMON STOCK:
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period																2.5
Balance, end of period		2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5		2.5	2.5	2.5
As reported | ADDITIONAL PAID-IN CAPITAL:
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period																802.2
Balance, end of period		847.2	847.2	847.2	847.2	802.2	802.2	802.2	847.2	802.2	847.2	802.2		847.2	802.2	802.2
As reported | ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS):
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period				(11.9)				11.4	(11.9)	11.4	(11.9)	11.4	(11.9)	11.4	2.6
Other comprehensive income (loss)				(2.9)				(16.0)	29.4	(16.0)	20.7	(5.8)		(23.3)	8.8
Balance, end of period		8.8	17.5	(14.8)	(11.9)	5.6	(4.6)	(4.6)	17.5	(4.6)	8.8	5.6		(11.9)	11.4
As reported | RETAINED EARNINGS (ACCUMULATED DEFICIT):
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period				(465.3)				(521.0)	(465.3)	(521.0)	(465.3)	(521.0)	(465.3)	(521.0)	(383.3)
Net income (loss)				(16.8)				(20.4)	(14.0)	(15.8)	(10.7)	(31.0)		55.7	(137.7)
Balance, end of period		(476.0)	(479.3)	(482.1)	(465.3)	(552.0)	(536.8)	(541.4)	(479.3)	(536.8)	(476.0)	(552.0)		(465.3)	(521.0)
Correction of errors
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period				8.9				(1.6)	8.9	(1.6)	8.9	(1.6)	8.9	(1.6)	1.0
Net income (loss)				1.6				(5.1)	(5.2)	(5.2)	(3.7)	(4.2)		8.7	(1.4)
Change in stockholder’s equity				3.1				(1.6)	(6.3)	(4.3)	(3.0)	(2.7)		10.5	(2.6)
Balance, end of period		5.9	2.6	12.0	8.9	(4.3)	(5.9)	(3.2)	2.6	(5.9)	5.9	(4.3)		8.9	(1.6)
Correction of errors | COMMON STOCK:
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period																0
Balance, end of period		0	0	0	0	0	0	0	0	0	0	0		0	0	0
Correction of errors | ADDITIONAL PAID-IN CAPITAL:
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period																0
Balance, end of period		0	0	0	0	0	0	0	0	0	0	0		0	0	0
Correction of errors | ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS):
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period				(0.8)				(2.6)	(0.8)	(2.6)	(0.8)	(2.6)	(0.8)	(2.6)	(1.4)
Other comprehensive income (loss)				1.5				3.5	(1.1)	0.9	0.7	1.5		1.8	(1.2)
Balance, end of period		(0.1)	(1.9)	0.7	(0.8)	(1.1)	(1.7)	0.9	(1.9)	(1.7)	(0.1)	(1.1)		(0.8)	(2.6)
Correction of errors | RETAINED EARNINGS (ACCUMULATED DEFICIT):
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period				9.7				1.0	9.7	1.0	9.7	1.0	9.7	1.0	2.4
Net income (loss)				1.6				(5.1)	(5.2)	(5.2)	(3.7)	(4.2)		8.7	(1.4)
Balance, end of period		$ 6.0	$ 4.5	$ 11.3	$ 9.7	$ (3.2)	$ (4.2)	$ (4.1)	$ 4.5	$ (4.2)	$ 6.0	$ (3.2)		$ 9.7	$ 1.0