Fair Value (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Fair Value [Abstract]
Level 3 assets fair value	$ 41,000,000	$ 66,000,000	$ 93,000,000	$ 92,000,000
Upper limit percentage of Level 3 assets to total invested assets	0.50%
Long-term debt, carrying value	1,659,000,000	1,669,000,000
Long-term debt, fair value	1,834,000,000	1,746,000,000
Material transfers between Level 1 and Level 2	$ 0	$ 0	$ 0