Schedule 2 - Parent Company Financial Statements - Balance Sheets (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
ASSETS
Investments in Subsidiaries	$ 245,100,000	$ 253,000,000
Fixed Maturities at Fair Value (Cost: )	4,575,000,000	4,860,200,000
Equity Securities at Fair Value (Cost: 2013 – $4.7; 2012 – $4.9)	5,000,000	4,500,000
Short-term Investments	284,700,000	327,500,000
Cash	66,500,000	96,300,000	251,200,000	117,200,000
Other Receivables	193,100,000	206,100,000
Deferred Income Taxes	294,600,000	388,300,000
Other Assets	267,400,000	256,700,000
Total Assets	7,656,400,000	8,009,100,000
LIABILITIES AND SHAREHOLDERS’ EQUITY
Notes Payable	606,900,000	611,400,000
Liabilities for Income Taxes	8,300,000	21,500,000
Accrued Expenses and Other Liabilities	329,800,000	431,400,000
Total Liabilities	5,604,900,000	5,847,400,000
Shareholders’ Equity:
Additional Paid-in Capital	694,800,000	725,000,000
Retained Earnings	1,215,800,000	1,118,200,000
Accumulated Other Comprehensive Income	135,300,000	312,700,000
Total Shareholders’ Equity	2,051,500,000	2,161,700,000	2,116,600,000	2,023,100,000
Total Liabilities and Shareholders’ Equity	7,656,400,000	8,009,100,000
Parent Company [Member]
ASSETS
Investments in Subsidiaries	2,614,000,000	2,744,000,000
Equity Securities at Fair Value (Cost: 2013 – $4.7; 2012 – $4.9)	5,000,000	4,500,000
Short-term Investments	130,800,000	183,500,000
Cash	20,800,000	2,200,000	122,400,000	400,000
Other Receivables	4,900,000	7,200,000
Deferred Income Taxes	35,000,000	75,400,000
Other Assets	7,300,000	6,300,000
Total Assets	2,817,800,000	3,023,100,000
LIABILITIES AND SHAREHOLDERS’ EQUITY
Liabilities for Income Taxes	90,500,000	77,600,000
Liabilities for Benefit Plans	63,900,000	172,800,000
Accrued Expenses and Other Liabilities	5,000,000	5,100,000
Total Liabilities	766,300,000	861,400,000
Shareholders’ Equity:
Common Stock	5,600,000	5,800,000
Additional Paid-in Capital	694,800,000	725,000,000
Retained Earnings	1,215,800,000	1,118,200,000
Accumulated Other Comprehensive Income	135,300,000	312,700,000
Total Shareholders’ Equity	2,051,500,000	2,161,700,000
Total Liabilities and Shareholders’ Equity	2,817,800,000	3,023,100,000
Parent Company [Member] | Senior Notes, 6% Due May 15, 2017 [Member]
LIABILITIES AND SHAREHOLDERS’ EQUITY
Notes Payable	357,900,000	357,300,000
Parent Company [Member] | Senior Notes, 6% Due November 30, 2015 [Member]
LIABILITIES AND SHAREHOLDERS’ EQUITY
Notes Payable	$ 249,000,000	$ 248,600,000