Quarterly Operating Results (Unaudited) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Condensed Statement of Earnings
Revenues	$ 1,362	$ 1,443	$ 1,139	$ 1,148	$ 1,208	$ 1,538	$ 1,124	$ 1,087	$ 5,092	$ 4,957	$ 4,643
Net earnings, including noncontrolling interests	165	98	77	113	19	211	84	88	453	402	319
Net earnings attributable to shareholders	$ 158	$ 83	$ 110	$ 120	$ 50	$ 226	$ 99	$ 113	$ 471	$ 488	$ 342
Earnings Attributable to Shareholders per Common Share:
Basic (USD per share)	$ 1.77	$ 0.94	$ 1.23	$ 1.34	$ 0.55	$ 2.43	$ 1.02	$ 1.16	$ 5.27	$ 5.18	$ 3.37
Diluted (USD per share)	$ 1.73	$ 0.92	$ 1.20	$ 1.32	$ 0.54	$ 2.39	$ 1.01	$ 1.14	$ 5.16	$ 5.09	$ 3.32
Average number of Common Shares:
Basic (shares)	89.4	89.1	89.6	89.4	89.8	92.9	96.4	97.7	89.3	94.2	101.3
Diluted (shares)	91.4	91.0	91.5	91.0	91.4	94.6	98.0	99.4	91.2	95.9	102.9