Debt (Schedule of debt instruments) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Short term debt	$ 549	$ 13
Long term debt	2,011	2,557
Total debt	2,560	2,570
Senior notes 5.850%, face amount $549, due December 15, 2014
Long term debt		548
Senior notes 6.500%, face amount of $350, due August 15, 2016
Long term debt	349	348
Senior notes 6.950%, face amount $150, due January 15, 2018
Long term debt	149	149
Senior notes 7.350%, face amount $350, due November 15, 2019
Long term debt	348	348
Senior notes 5.875%, face amount $500, due August 15, 2020
Long term debt	497	496
Senior notes 5.750%, face amount $400, due August 15, 2021
Long term debt	397	397
Debenture of CNAF, 7.250%, face amount of $243, due November 15, 2023
Long term debt	241	241
Subordinated variable rate debt of Hardy, face amount of $30, due September 15, 2036
Long term debt	30	30
Other debt
Short term debt		13
Senior notes 5.850%, face amount $549, due December 15, 2014
Short term debt	$ 549