Consolidated Statements of Preferred Stock and Common Shareholders' Equity (USD $) In Millions, unless otherwise specified	Total	Convertible Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Unallocated ESSOP Shares [Member]
Beginning Balance at Dec. 31, 2010		$ 0	$ 259.2	$ 649.6	$ 2,791.4	$ 459.1	$ (38.0)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividend reinvestment plan			0	0.8
Net issuance of shares under stock based compensation plans			0	0
Conversion of senior debentures			0	0
Stock based compensation				3.4
ESSOP shares released				1.0			4.8
Acquisition of non-controlling interest				2.7
Net income (loss)	(140.5)				(140.5)
Dividends on common stock: cash					(178.4)
Net unrealized gains (losses) on securities, net of tax	7.5					7.5
Net adjustment related to defined benefit pension plans, net of tax	(36.2)					(36.2)
Foreign currency translation and other adjustments	(14.3)					(14.3)
Ending Balance at Dec. 31, 2011		0	259.3	657.9	2,472.4	416.0	(33.2)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividend reinvestment plan			0	0.8
Net issuance of shares under stock based compensation plans			0	(0.6)
Conversion of senior debentures			0	0
Stock based compensation				2.5
ESSOP shares released				0.3			5.0
Acquisition of non-controlling interest				0
Net income (loss)	(68.6)				(68.6)
Dividends on common stock: cash					(181.5)
Net unrealized gains (losses) on securities, net of tax	73.8					73.8
Net adjustment related to defined benefit pension plans, net of tax	(12.6)					(12.6)
Foreign currency translation and other adjustments	4.4					4.4
Ending Balance at Dec. 31, 2012	3,596.2	0	259.4	660.9	2,222.3	481.7	(28.2)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividend reinvestment plan			0	0.8
Net issuance of shares under stock based compensation plans			0.9	9.5
Conversion of senior debentures			0	0
Stock based compensation				0
ESSOP shares released				2.6			5.2
Acquisition of non-controlling interest				0
Net income (loss)	447.8				447.8
Dividends on common stock: cash					(184.8)
Net unrealized gains (losses) on securities, net of tax	(166.2)					(166.2)
Net adjustment related to defined benefit pension plans, net of tax	72.6					72.6
Foreign currency translation and other adjustments	(9.9)					(9.9)
Ending Balance at Dec. 31, 2013	$ 3,775.0	$ 0	$ 260.4	$ 673.9	$ 2,485.3	$ 378.2	$ (23.0)