Stock Based Compensation (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Feb. 01, 2016	Dec. 31, 2011	Dec. 31, 2009	Dec. 31, 2002
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	$ 173,000,000	$ 181,000,000	$ 154,000,000
Total tax benefit recognized related to share-based compensation expense	63,000,000	$ 66,000,000	$ 56,000,000
Unamortized share-based compensation expense related to nonvested equity compensation arrangements	$ 191,000,000
Period over which unamortized share-based compensation expense will be amortized.	5 years
Maximum life of options (in years)	10 years
Options exercisable at end of period - Common stock		6,810,000	10,204,000
Options exercisable at end of the period - weighted average price		$ 82.86	$ 89.46
Total intrinsic value of options exercised	$ 62,000,000	$ 90,000,000	$ 86,000,000
Cash received from option exercises under all Incentive Plans	103,000,000	215,000,000	208,000,000
Tax benefit realized from option exercises under all Incentive Plans	$ 23,000,000	$ 33,000,000	$ 31,000,000
Shares of common stock available for next year, Granting of options under Incentive Plans	14,000,000
Total common stock authorized for future issuance under equity compensation plans	15,000,000
Treasury stock	1,200,000
Deferred stock units awards granted to non-employee directors	18,048	21,490	27,076
Vesting period for restricted share/restricted share unit awards, lower range	3 years
Vesting period for restricted share/restricted share unit awards, upper range	5 years
Weighted-average grant date fair value of incentive/performance unit awards and restricted share/restricted share unit awards granted	$ 91.57	$ 80.79	$ 64.77
Total intrinsic value of incentive/performance unit and restricted share/restricted share unit awards vested during the year.	$ 175,000,000	$ 119,000,000	$ 63,000,000
Total share-based liability awards paid out during the year	$ 41,000,000	$ 38,000,000	$ 29,000,000
ESPP - shares available for issuance	1,000,000
ESPP - Fair market value purchase rate of common stock (percent)	95.00%
BlackRock Series C Preferred Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
LTIP - Number of preferred shares acquired in exchange agreement						2,900,000
LTIP - Number of preferred stock shares transferred			200,000	500,000	1,300,000
LTIP - Total preferred shares held at end of period	1,300,000	1,300,000
BlackRock LTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
LTIP - Number of committed shares to be released							4,000,000
LTIP - Number of common stock shares transferred							1,100,000
Total - Nonvested Cash Payable Incentive/Performance Units and Restricted Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate intrinsic value - liability awards	$ 74,000,000