Consolidated Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 66.1	$ 193.9	$ 260.5	$ 250.2
Unrealized gains (losses) on securities:
Unrealized gains (losses) on securities before reclassifications	145.0	(230.4)	251.4	(121.3)
Amounts reclassified as realized investment gains from sales in the statements of income	(49.9)	(137.1)	(241.2)	(141.7)
Pretax unrealized gains (losses) on securities	95.1	(367.6)	10.1	(263.0)
Deferred income taxes (credits)	33.2	(128.4)	3.4	(91.8)
Net unrealized gains (losses) on securities, net of tax	61.8	(239.2)	6.7	(171.2)
Defined benefit pension plans:
Net pension adjustment before reclassifications	0	0	0	0
Amounts reclassified as underwriting, acquisition, and other expenses in the statements of income	(0.4)	2.9	(0.9)	5.8
Net adjustment related to defined benefit pension plans	(0.4)	2.9	(0.9)	5.8
Deferred income taxes (credits)	(0.1)	1.0	(0.3)	2.0
Net adjustment related to defined benefit pension plans, net of tax	(0.3)	1.8	(0.6)	3.7
Foreign currency translation and other adjustments	2.2	(4.4)	(1.0)	(7.6)
Net adjustments	63.7	(241.7)	5.0	(175.1)
Comprehensive Income (Loss)	$ 129.9	$ (47.8)	$ 265.6	$ 75.0