Consolidated Statements Of Income And Comprehensive Income (USD $) In Millions, except Share data	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Revenues:
Premiums	$ 539.8	$ 532.8	$ 1,610.6	$ 1,573.2
Administrative fees	28.5	29.1	87.4	86.7
Net investment income	147.3	152.7	456.9	444.5
Net capital gains (losses):
Total other-than-temporary impairment losses on fixed maturity securities-available-for-sale	(0.3)	(0.6)	(1.7)	(0.7)
All other net capital losses	8.0	(29.0)	(6.2)	(48.8)
Net capital gains (losses)	7.7	(29.6)	(7.9)	(49.5)
Total revenues	723.3	685.0	2,147.0	2,054.9
Benefits and expenses:
Benefits to policyholders	432.2	400.9	1,324.7	1,207.7
Interest credited	36.7	44.1	117.1	116.6
Operating expenses	120.7	108.5	357.1	334.8
Commissions and bonuses	53.1	51.5	166.1	154.6
Premium taxes	9.1	8.4	27.4	26.1
Interest expense	9.7	9.7	29.2	29.2
Net increase in deferred acquisition costs, value of business acquired and other intangible assets	(4.9)	(7.7)	(17.3)	(20.6)
Total benefits and expenses	656.6	615.4	2,004.3	1,848.4
Income before income taxes	66.7	69.6	142.7	206.5
Income taxes	19.2	23.4	42.7	69.5
Net income	47.5	46.2	100.0	137.0
Other Comprehensive income, net of tax:
Net unrealized capital gains on securities-available-for-sale	73.5	78.4	99.5	204.3
Reclassification adjustment for net capital gains included in net income	(0.7)	(1.9)	(4.7)	(7.5)
Employee benefit plans:
Prior service credit (cost) and net losses arising during the period, net	0	0	1.5	(2.5)
Reclassification adjustment for amortization to net periodic pension cost, net	0.9	0.9	2.5	2.7
Total other comprehensive income, net of tax	73.7	77.4	98.8	197.0
Comprehensive income	$ 121.2	$ 123.6	$ 198.8	$ 334.0
Net income per common share:
Basic	$ 1.07	$ 0.99	$ 2.22	$ 2.91
Diluted	$ 1.07	$ 0.99	$ 2.21	$ 2.90
Weighted-average common shares outstanding:
Basic	44,521,757	46,443,127	45,102,716	47,023,419
Diluted	44,577,667	46,607,410	45,256,407	47,255,157