Stockholders' Equity and Statutory Accounting Practices (Combined statutory capital and surplus and net income (loss)) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Combined Continental Casualty Companies [Member]
Statutory Accounting
Statutory capital and surplus	$ 9,888	[1],[2]	$ 9,821	[1]
Statutory net income (loss)	954	[1],[2]	258	[1]	17	[1]
Life Company [Member]
Statutory Accounting
Statutory capital and surplus	519	[2]	498
Statutory net income (loss)	$ 29	[2]	$ 86		$ (65)

[1] Represents the combined statutory surplus of CCC and its subsidiaries, including the Life company.

[2] Preliminary.