CONSOLIDATED STATEMENT OF SHAREHOLDERS' EQUITY (USD $) In Millions, unless otherwise specified	Total	Common stock and additional paid-in capital	Accumulated other comprehensive income	Retained earnings (accumulated deficit)
Balance, beginning of period at Dec. 31, 2012	$ 5,049.3	$ 4,176.9	$ 1,197.4	$ (325.0)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	89.0	0	0	89.0
Change in unrealized appreciation (depreciation) of investments (net of applicable income tax expense (benefit))	(497.9)	0	(497.9)	0
Change in noncredit component of impairment losses on fixed maturities, available for sale (net of applicable income tax expense (benefit))	(1.4)	0	(1.4)	0
Extinguishment of beneficial conversion feature related to the repurchase of convertible debentures	(12.6)	(12.6)	0	0
Cost of shares acquired	(50.0)	(50.0)	0	0
Dividends on common stock	(11.1)	0	0	(11.1)
Stock Based Compensation	16.1	16.1	0	0
Balance, end of period at Jun. 30, 2013	4,581.4	4,130.4	698.1	(247.1)
Balance, beginning of period at Dec. 31, 2013	4,955.2	4,095.0	731.8	128.4
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(149.9)	0	0	(149.9)
Change in unrealized appreciation (depreciation) of investments (net of applicable income tax expense (benefit))	193.7	0	193.7	0
Change in noncredit component of impairment losses on fixed maturities, available for sale (net of applicable income tax expense (benefit))	0.6	0	0.6	0
Cost of shares acquired	(136.6)	(136.6)	0	0
Dividends on common stock	(26.3)	0	0	(26.3)
Stock Based Compensation	7.6	7.6	0	0
Balance, end of period at Jun. 30, 2014	$ 4,844.3	$ 3,966.0	$ 926.1	$ (47.8)