Condensed Consolidating Financial Statements - Condensed Consolidating Statements Of Cash Flows (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Condensed Consolidating Financial Information [Line Items]
Net cash provided by operating activities	$ 3,728		$ 3,111		$ 2,606
Cash flows from investing activities - continuing operations:
Capital expenditures	(521)		(436)		(436)
Business acquisitions, net of cash acquired					(444)
Purchases of held-to-maturity securities	(500)		0		(260)
Net cash used by investing activities	(1,102)		(363)		(642)
Cash flows from financing activities - continuing operations:
Purchases of common stock	0		0		2,382
Purchases of common stock	(3,382)		(740)		(602)
Dividends paid	(822)		(591)		(893)
Proceeds from option exercises	547		583		146
Net cash used by financing activities	(3,575)		(725)		(1,382)
Net cash provided (used) by discontinued operations	36		(18)		65
Net (decrease) increase in cash and equivalents	(913)		2,005		647
Cash and equivalents at beginning of year	5,301		3,296		2,649
Cash and equivalents at end of year	4,388		5,301		3,296
Parent
Condensed Consolidating Financial Information [Line Items]
Net cash provided by operating activities	(296)	[1]	(454)	[1]	(541)	[1]
Cash flows from investing activities - continuing operations:
Capital expenditures	(71)		(1)		(2)
Business acquisitions, net of cash acquired					(121)
Purchases of held-to-maturity securities	(500)
Other, net	3		3		221
Net cash used by investing activities	(568)		2		98
Cash flows from financing activities - continuing operations:
Purchases of common stock					2,382
Purchases of common stock	(3,382)		(740)		(602)
Repayment of fixed-rate notes					(2,400)
Dividends paid	(822)		(591)		(893)
Proceeds from option exercises	547		583
Other, net	83		23		154
Net cash used by financing activities	(3,574)		(725)		(1,359)
Net cash provided (used) by discontinued operations	36		(18)		65
Cash sweep/funding by parent	2,759		3,074		2,465
Net (decrease) increase in cash and equivalents	(1,643)		1,879		728
Cash and equivalents at beginning of year	4,179		2,300		1,572
Cash and equivalents at end of year	2,536		4,179		2,300
Guarantors on a Combined Basis
Condensed Consolidating Financial Information [Line Items]
Net cash provided by operating activities	2,798	[1]	2,810	[1]	2,850	[1]
Cash flows from investing activities - continuing operations:
Capital expenditures	(409)		(381)		(390)
Business acquisitions, net of cash acquired					(297)
Purchases of held-to-maturity securities	0
Other, net	(74)		59		(1)
Net cash used by investing activities	(483)		(322)		(688)
Cash flows from financing activities - continuing operations:
Purchases of common stock					0
Purchases of common stock	0		0		0
Repayment of fixed-rate notes					0
Dividends paid	0		0		0
Proceeds from option exercises	0		0
Other, net	(1)		0		(21)
Net cash used by financing activities	(1)		0		(21)
Net cash provided (used) by discontinued operations	0		0		0
Cash sweep/funding by parent	(2,314)		(2,488)		(2,141)
Net (decrease) increase in cash and equivalents	0		0		0
Cash and equivalents at beginning of year	0		0		0
Cash and equivalents at end of year	0		0		0
Other Subsidiaries on a Combined Basis
Condensed Consolidating Financial Information [Line Items]
Net cash provided by operating activities	1,226	[1]	755	[1]	297	[1]
Cash flows from investing activities - continuing operations:
Capital expenditures	(41)		(54)		(44)
Business acquisitions, net of cash acquired					(26)
Purchases of held-to-maturity securities	0
Other, net	(10)		11		18
Net cash used by investing activities	(51)		(43)		(52)
Cash flows from financing activities - continuing operations:
Purchases of common stock					0
Purchases of common stock	0		0		0
Repayment of fixed-rate notes					0
Dividends paid	0		0		0
Proceeds from option exercises	0		0
Other, net	0		0		(2)
Net cash used by financing activities	0		0		(2)
Net cash provided (used) by discontinued operations	0		0		0
Cash sweep/funding by parent	(445)		(586)		(324)
Net (decrease) increase in cash and equivalents	730		126		(81)
Cash and equivalents at beginning of year	1,122		996		1,077
Cash and equivalents at end of year	1,852		1,122		996
Consolidating Adjustments
Condensed Consolidating Financial Information [Line Items]
Net cash provided by operating activities	0	[1]	0	[1]	0	[1]
Cash flows from investing activities - continuing operations:
Capital expenditures	0		0		0
Business acquisitions, net of cash acquired					0
Purchases of held-to-maturity securities	0
Other, net	0		0		0
Net cash used by investing activities	0		0		0
Cash flows from financing activities - continuing operations:
Purchases of common stock					0
Purchases of common stock	0		0		0
Repayment of fixed-rate notes					0
Dividends paid	0		0		0
Proceeds from option exercises	0		0
Other, net	0		0		0
Net cash used by financing activities	0		0		0
Net cash provided (used) by discontinued operations	0		0		0
Cash sweep/funding by parent	0		0		0
Net (decrease) increase in cash and equivalents	0		0		0
Cash and equivalents at beginning of year	0		0		0
Cash and equivalents at end of year	0		0		0
Total Consolidated
Condensed Consolidating Financial Information [Line Items]
Net cash provided by operating activities	3,728	[1]	3,111	[1]	2,606	[1]
Cash flows from investing activities - continuing operations:
Capital expenditures	(521)		(436)		(436)
Business acquisitions, net of cash acquired					(444)
Purchases of held-to-maturity securities	(500)
Other, net	(81)		73		238
Net cash used by investing activities	(1,102)		(363)		(642)
Cash flows from financing activities - continuing operations:
Purchases of common stock					2,382
Purchases of common stock	(3,382)		(740)		(602)
Repayment of fixed-rate notes					(2,400)
Dividends paid	(822)		(591)		(893)
Proceeds from option exercises	547		583
Other, net	82		23		131
Net cash used by financing activities	(3,575)		(725)		(1,382)
Net cash provided (used) by discontinued operations	36		(18)		65
Cash sweep/funding by parent	0		0		0
Net (decrease) increase in cash and equivalents	(913)		2,005		647
Cash and equivalents at beginning of year	5,301		3,296		2,649
Cash and equivalents at end of year	$ 4,388		$ 5,301		$ 3,296

[1] * Continuing operations only.