Schedule I-Parent Company Financial Information (Condensed Statements Of Cash Flows) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Net cash provided by operating activities	$ 2,079	$ 2,242	$ 1,422
Acquisitions	(226)	(833)	(12)
Purchases of investment securities	(3,678)	(4,589)	(7,197)
Proceeds from sale of investment securities	1,259	2,012	3,951
Maturities of investment securities	1,569	1,750	1,271
Purchases of property and equipment, net	(346)	(222)	(185)
Change in securities lending collateral	54	71	312
Net cash used in investing activities	(1,358)	(1,811)	(1,859)
Repayments under credit agreement	0	0	(250)
Change in book overdraft	(103)	35	150
Change in securities lending payable	(56)	(71)	(312)
Common stock repurchases	(541)	(108)	(23)
Dividends paid	(82)	0	0
Tax benefit from stock-based compensation	15	2	5
Proceeds from stock option exercises and other	128	8	17
Net cash (used in) provided by financing activities	(1,017)	(371)	80
(Decrease) increase in cash and cash equivalents	(296)	60	(357)
Cash and cash equivalents at beginning of year	1,673	1,613	1,970
Cash and cash equivalents at end of year	1,377	1,673	1,613
Parent Company [Member]
Net cash provided by operating activities	1,106	1,219	911
Acquisitions	(223)	(840)	(6)
Purchases of investment securities	(632)	(633)	(597)
Proceeds from sale of investment securities	10	16	2
Maturities of investment securities	548	697	278
Purchases of property and equipment, net	(225)	(166)	(143)
Capital contributions to operating subsidiaries	(214)	(230)	(132)
Change in securities lending collateral	0	1	0
Net cash used in investing activities	(736)	(1,155)	(598)
Repayments under credit agreement	0	0	(250)
Change in book overdraft	(21)	2	35
Change in securities lending payable	0	(1)	0
Common stock repurchases	(541)	(108)	(23)
Dividends paid	(82)	0	0
Tax benefit from stock-based compensation	15	2	5
Proceeds from stock option exercises and other	132	9	17
Net cash (used in) provided by financing activities	(497)	(96)	(216)
(Decrease) increase in cash and cash equivalents	(127)	(32)	97
Cash and cash equivalents at beginning of year	314	346	249
Cash and cash equivalents at end of year	$ 187	$ 314	$ 346