Accumulated Other Comprehensive Income (Details Textual) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Accumulated Other Comprehensive Income (Textual) [Abstract]
Net unrealized holding (losses) arising during period, tax	$ 203	$ 198	$ 127	$ 132
Reclassification adjustment for (gains) realized in net income, tax	(27)	(5)	(39)	(23)
Maximum Reclassification adjustment for losses realized in net income, tax			1	1
Net gains (losses) arising during period, tax	(29)	(25)	(5)	(28)
Reclassification adjustment for losses realized in net income, tax	2	1	3	2
Maximum change in unfunded pension postretirement liability, tax	1	1	1	1
Amortization of prior service cost and transition obligation included in net income, tax	$ 1	$ 1	$ 1	$ 1