Summary of Significant Accounting Policies Income Taxes (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Taxes [Abstract]
Statutory tax rate	35.00%	(35.00%)	(35.00%)
Tax-Exempt interest	(0.40%)	(4.10%)	(5.40%)
Dividends received exclusion	(0.60%)	(2.10%)	(1.00%)
Valuation allowance	0.00%	(2.00%)	(0.60%)
Goodwill impairment	0.00%	0.40%	1.60%
Foreign income (loss) reattribution	(0.20%)	(3.50%)	1.00%
Sale of subsidiary	0.00%	(1.30%)	0.00%
Other items - net	(0.40%)	1.00%	(1.20%)
Effective tax rates (credit)	33.40%	(46.60%)	(40.60%)
Deferred Tax Assets [Abstract]
Deferred Tax Assets, losses, claims, and settlement expenses	$ 286.9	$ 272.4	$ 231.7
Deferred Tax Assets, Pension and deferred compensation plans	51.3	90.8	85.8
Deferred Tax Assets, Impairment losses on investments	3.2	49.2	52.9
Deferred Tax Assets, Net operating loss carryforward	43.7	91.0	77.2
Deferred Tax Assets, AMT credit carryforward	9.6	25.5	29.7
Deferred Tax Assets, Other temporary differences	50.5	67.7	50.1
Total deferred tax assets before valuation allowance	445.3	596.8	527.7
Deferred Tax Assets, Valuation allowance	(9.6)	(9.6)	(12.2)
Total deferred tax assets	435.7	587.2	515.4
Deferred Tax Liabilities [Abstract]
Deferred Tax Liabilties, Unearned premium reserves	42.7	35.3	29.3
Deferred Tax Liabilities, Deferred policy acquisition costs	63.1	52.5	63.9
Deferred Tax Liabilities, Mortgage guaranty insurers' contingency reserves	20.1	0	0.4
Deferred Tax Liabilities, Amortization of fixed maturity securities	4.9	6.9	7.2
Deferred Tax Liabilities, Net unrealized investment gains	220.5	309.7	273.0
Deferred Tax Liabilities, Title plants and records	4.9	5.0	5.0
Deferred Tax Liabilities, Other temporary differences	30.6	29.6	19.7
Total deferred tax liabilities	387.1	439.2	398.7
Net deferred tax assets (liabilities)	48.4	148.1	116.7
Operating loss carryforwards	124.8
Contingency reserve deduction	57.6
US Treasury Tax and Loss Bonds to be acquired	$ 20.1