Retirement Plans and Profit Sharing Arrangements (Details 4) (USD $) In Millions, unless otherwise specified	1 Months Ended	2 Months Ended	4 Months Ended	12 Months Ended
	Mar. 31, 2010	Feb. 28, 2010	Apr. 30, 2009	Dec. 31, 2011 D Y	Dec. 31, 2010	Dec. 31, 2009
Summary of unrealized losses included in other comprehensive income
Net unrealized defined benefit losses at the beginning of the period		$ 20	$ 39	$ 24	$ 20	$ 39
Net gains (losses)				(77)	(4)	15
Prior service cost (credit)				(2)	(2)	14
Income tax benefit (provision)				28	2	(10)
Net unrealized defined benefit losses at the at the end of the period				75	24	20
Percentage of matching contribution by an employer effective March 1, 2010	100.00%
Percent of compensation effective March 1, 2010 eligible for matching contribution by employer	5.00%
Percentage of matching contribution by an employer prior to March 1, 2010		100.00%
Percent of compensation prior to March 1, 2010 eligible for matching contribution by employer		3.00%
Percentage of base pay contributed by the employer before May 2009			1.00%
Minimum service period for eligibility under the defined contribution plan (in days)				60
Period of graded schedule for vesting fixed and variable match contributions and stock contributions (in years)				5
Defined contribution plan expense				33	32	16
Profit sharing plan
Threadneedle Profit Sharing Arrangements
Percentage of profit sharing				30.00%
Compensation expense (benefit) related to the employee profit sharing plan				$ 54	$ 52	$ 32