Fair Value (Text Items) (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Fair Value Disclosures [Abstract]
Total assets and liabilities measured at fair value	$ 12,750,000,000		$ 12,400,000,000
Total assets and liabilities measured at fair value priced using non-binding broker quotes	1,100,000,000		927,900,000
Total assets and liabilities measured at fair value priced using non-binding broker quotes (percentage)	8.60%		7.50%
Gains (losses) including in earnings attributable to the change in unrealized gains or losses related to assets still held at balance sheet date	6,600,000	2,400,000
Senior notes	300,000,000		300,000,000
Estimated fair value of senior notes	$ 387,500,000