SCHEDULE II - BASIS OF PRESENTATION - BALANCE SHEET (DETAILS) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Condensed Financial Statements, Captions [Line Items]
Total assets	$ 34,131.4	$ 32,921.9
Accumulated other comprehensive income (loss)	1,197.4	781.6
Retained earnings (accumulated deficit)	(325.0)	(532.1)
Total shareholders' equity	5,049.3	4,613.8	3,811.6	3,038.6
Total liabilities and shareholders' equity	34,131.4	32,921.9
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Investment in wholly-owned subsidiaries	6,034.5	5,488.6
Total assets	6,351.4	5,764.5
Accumulated other comprehensive income (loss)	1,197.4	781.6
Retained earnings (accumulated deficit)	(325.0)	(532.1)
Total shareholders' equity	5,049.3	4,613.8
Total liabilities and shareholders' equity	6,351.4	5,764.5
Previously Reported [Member]
Condensed Financial Statements, Captions [Line Items]
Total assets		33,332.7
Accumulated other comprehensive income (loss)		625.5
Retained earnings (accumulated deficit)		42.8
Total shareholders' equity		5,032.6
Total liabilities and shareholders' equity		33,332.7
Previously Reported [Member] | Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Investment in wholly-owned subsidiaries		5,907.4
Total assets		6,183.3
Accumulated other comprehensive income (loss)		625.5
Retained earnings (accumulated deficit)		42.8
Total shareholders' equity		5,032.6
Total liabilities and shareholders' equity		6,183.3
Adjustments for New Accounting Pronouncement [Member]
Condensed Financial Statements, Captions [Line Items]
Total assets		(410.8)
Accumulated other comprehensive income (loss)		156.1
Retained earnings (accumulated deficit)		(574.9)
Total shareholders' equity		(418.8)
Total liabilities and shareholders' equity		(410.8)
Adjustments for New Accounting Pronouncement [Member] | Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Investment in wholly-owned subsidiaries		(418.8)
Total assets		(418.8)
Accumulated other comprehensive income (loss)		156.1
Retained earnings (accumulated deficit)		(574.9)
Total shareholders' equity		(418.8)
Total liabilities and shareholders' equity		$ (418.8)