Schedule II - Condensed Financial Information of Registrant Statements of Cash Flows (details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash flows from operating activities:
Net income (loss)	$ 447.8	$ (68.6)	$ (140.5)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Income taxes - net	103.7	(60.7)	(88.5)
Accounts payable, accrued expenses and other	67.3	98.6	111.2
Total	686.7	532.0	(94.9)
Cash flows from investing activities:
Maturities and early calls	1,387.4	1,080.3	926.8
Net decrease (increase) in short-term investments	139.1	211.5	(476.0)
Total	(457.6)	(3.7)	(187.1)
Cash flows from financing activities:
Issuance of debentures and notes	0	0	537.0
Issuance of common shares	11.8	1.0	1.2
Redemption of debentures and notes	(3.6)	(339.8)	(112.1)
Dividends on common shares	(184.8)	(181.5)	(178.4)
Other - net	(0.3)	0.2	0.1
Total	(176.9)	(520.0)	247.8
Increase (decrease) in cash:	52.0	8.1	(34.2)
Cash, beginning of year	101.2	93.0	127.3
Cash, end of year	153.3	101.2	93.0
Parent Company [Member]
Cash flows from operating activities:
Net income (loss)	447.8	(68.6)	(140.5)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Accounts receivable	(0.7)	0.2	(0.1)
Income taxes - net	24.5	(83.8)	55.9
Excess of equity in net (income) loss of subsidiaries over cash dividends received	(240.1)	262.6	305.3
Accounts payable, accrued expenses and other	(2.0)	6.4	10.9
Total	229.5	116.7	231.5
Cash flows from investing activities:
Maturities and early calls	10.0	0	0
Purchases of Fixed assets for company use	(2.3)	(1.4)	(4.3)
Net repayment (issuance) of notes to related parties	(87.4)	380.0	(564.4)
Net decrease (increase) in short-term investments	21.4	(44.4)	(18.6)
Total	(58.3)	334.0	(587.4)
Cash flows from financing activities:
Issuance of debentures and notes	0	0	537.0
Net receipt (repayment) of notes and loans from related parties	25.0	49.0	(1.5)
Issuance of common shares	11.8	1.0	1.2
Redemption of debentures and notes	(2.7)	(318.7)	(2.3)
Dividends on common shares	(184.8)	(181.5)	(178.4)
Other - net	(0.4)	(0.6)	(0.1)
Total	(151.1)	(450.8)	355.8
Increase (decrease) in cash:	20.0	0	0
Cash, beginning of year	0	0	0
Cash, end of year	$ 20.1	$ 0	$ 0