Restructuring Charges (Schedule of Changes in Restructuring Reserves) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Restructuring Cost and Reserve [Line Items]
Balance at beginning of period		$ 50		$ 0
Restructuring charges		20	$ 0	73	$ 0
Payments		(21)		(24)
Adjustments for non-cash charges	[1]	(2)		(2)
Balance at end of period		47		47
Total restructuring charges incurred to date		73		$ 73
Expected completion date of restructuring activities				Dec. 31, 2018
Employee costs
Restructuring Cost and Reserve [Line Items]
Balance at beginning of period		46		$ 0
Restructuring charges		4		50
Payments		(12)		(12)
Adjustments for non-cash charges	[1]	2		2
Balance at end of period		40		40
Total restructuring charges incurred to date		50		50
Facilities costs
Restructuring Cost and Reserve [Line Items]
Balance at beginning of period		0		0
Restructuring charges		5		5
Payments		(1)		(1)
Adjustments for non-cash charges	[1]	(4)		(4)
Balance at end of period		0		0
Total restructuring charges incurred to date		5		5
Technology costs
Restructuring Cost and Reserve [Line Items]
Balance at beginning of period		0		0
Restructuring charges		0		0
Payments		0		0
Adjustments for non-cash charges	[1]	0		0
Balance at end of period		0		0
Total restructuring charges incurred to date		0		0
Other costs
Restructuring Cost and Reserve [Line Items]
Balance at beginning of period		4		0
Restructuring charges		11		18
Payments		(8)		(11)
Adjustments for non-cash charges	[1]	0		0
Balance at end of period		7		7
Total restructuring charges incurred to date		18		18
Minimum
Restructuring Cost and Reserve [Line Items]
Total expected restructuring charges	[2]	140		140
Minimum | Employee costs
Restructuring Cost and Reserve [Line Items]
Total expected restructuring charges	[2]	65		65
Minimum | Facilities costs
Restructuring Cost and Reserve [Line Items]
Total expected restructuring charges	[2]	35		35
Minimum | Technology costs
Restructuring Cost and Reserve [Line Items]
Total expected restructuring charges	[2]	10		10
Minimum | Other costs
Restructuring Cost and Reserve [Line Items]
Total expected restructuring charges	[2]	30		30
Maximum
Restructuring Cost and Reserve [Line Items]
Total expected restructuring charges	[2]	160		160
Maximum | Employee costs
Restructuring Cost and Reserve [Line Items]
Total expected restructuring charges	[2]	70		70
Maximum | Facilities costs
Restructuring Cost and Reserve [Line Items]
Total expected restructuring charges	[2]	40		40
Maximum | Technology costs
Restructuring Cost and Reserve [Line Items]
Total expected restructuring charges	[2]	15		15
Maximum | Other costs
Restructuring Cost and Reserve [Line Items]
Total expected restructuring charges	[2]	$ 35		$ 35

[1] Adjustments for non-cash charges include the benefit from forfeitures of nonvested stock compensation in Employee Costs and accelerated depreciation expense in Facilities Costs.

[2] Restructuring activities are expected to be substantially completed by 12/31/2018.