Consolidated Statements Of Cash Flows (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 49.7	$ 29.3
Adjustments to reconcile net income to net cash provided by operating activities:
Loss from retirement of debt		2.5
Net realized investment gains	(2.3)	(2.9)
Net amortization and depreciation	9.1	4.2
Stock-based compensation expense	4.1	3.6
Amortization of deferred benefit plan costs	2.3	2.6
Deferred income taxes	(18.9)	5.6
Change in deferred acquisition costs	(9.4)	5.4
Change in premiums receivable, net of reinsurance premiums payable	49.3	15.5
Change in loss, loss adjustment expense and unearned premium reserves	138.8	25.8
Change in reinsurance recoverable	(167.9)	(14.4)
Change in expenses and taxes payable	(28.2)	(64.5)
Other, net	(13.9)	11.5
Net cash provided by operating activities	12.7	24.2
CASH FLOWS FROM INVESTING ACTIVITIES
Proceeds from disposals and maturities of fixed maturities	550.9	283.1
Proceeds from disposals of equity securities and other investments	2.6	0.7
Purchases of fixed maturities	(663.0)	(304.5)
Purchases of equity securities and other investments	(98.4)	(14.7)
Capital expenditures	(3.2)	(2.1)
Net cash used in investing activities	(211.1)	(37.5)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from exercise of employee stock options	1.1	3.9
Proceeds from debt borrowings	7.4	3.0
Change in collateral related to securities lending program	(7.8)	(3.8)
Dividends paid to shareholders	(13.5)	(12.5)
Repurchases of debt	(0.8)	(50.5)
Other financing activities	(0.2)	(0.6)
Net cash used in financing activities	(13.8)	(60.5)
Effect of exchange rate changes on cash	20.1
Net change in cash and cash equivalents	(192.1)	(73.8)
Net change in cash related to discontinued operations		2.2
Cash and cash equivalents, beginning of period	820.4	290.4
Cash and cash equivalents, end of period	$ 628.3	$ 218.8