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, 2013		Dec. 31, 2012		Dec. 31, 2011
Combined Continental Casualty Companies [Member]
Statutory Accounting Practices [Line Items]
Statutory capital and surplus	$ 11,137	[1],[2]	$ 9,998	[1]
Statutory net income (loss)	913	[1],[2]	391	[1]	954	[1]
Life Company [Member]
Statutory Accounting Practices [Line Items]
Statutory capital and surplus	597	[2]	556
Statutory net income (loss)	$ 48	[2]	$ 44		$ 29

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

[2] Information derived from the statutory-basis financial statements to be filed with insurance regulators.