Condensed Consolidating Statements Of Cash Flows (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Condensed Consolidating Financial Information [Line Items]
Net cash provided by operating activities	$ 2,687	$ 3,238	$ 2,986
Cash flows from investing activities:
Maturities of held-to-maturity securities	224	441	605
Purchases of available-for-sale securities	(252)	(373)	(226)
Purchases of held-to-maturity securities	(260)	(459)	(468)
Capital expenditures	(450)	(458)	(370)
Business acquisitions, net of cash acquired	(444)	(1,560)	(233)
Sales of held-to-maturity securities	211	0	0
Other, net	238	435	(175)
Net cash used by investing activities	(656)	(1,974)	(408)
Cash flows from financing activities:
Proceeds from fixed-rate notes	2,382	1,497
Purchases of common stock	(602)	(1,468)	(1,185)
Repayment of fixed-rate notes	(2,400)	(750)	(700)
Dividends paid	(893)	(673)	(631)
Proceeds from option exercises	146	198	277
Other, net	131	193	290
Net cash used by financing activities	(1,382)	(1,201)	(2,226)
Net cash used by discontinued operations	(2)	(27)	(2)
Cash sweep/funding by parent	0	0	0
Net increase in cash and equivalents	647	36	350
Cash and equivalents at beginning of year	2,649	2,613	2,263
Cash and equivalents at end of year	3,296	2,649	2,613
Parent
Condensed Consolidating Financial Information [Line Items]
Net cash provided by operating activities	(541)	(359)	(391)
Cash flows from investing activities:
Maturities of held-to-maturity securities		334	273
Purchases of available-for-sale securities		(274)
Purchases of held-to-maturity securities		(459)	(237)
Capital expenditures	(2)	(6)	(10)
Business acquisitions, net of cash acquired	(121)	(233)
Other, net	221	246	(12)
Net cash used by investing activities	98	(392)	14
Cash flows from financing activities:
Proceeds from fixed-rate notes	2,382	1,497
Purchases of common stock	(602)	(1,468)	(1,185)
Repayment of fixed-rate notes	(2,400)	(750)	(700)
Dividends paid	(893)	(673)	(631)
Other, net	154	216	295
Net cash used by financing activities	(1,359)	(1,178)	(2,221)
Net cash used by discontinued operations	(2)	0	0
Cash sweep/funding by parent	2,522	1,851	2,800
Net increase in cash and equivalents	718	(78)	202
Cash and equivalents at beginning of year	1,530	1,608	1,406
Cash and equivalents at end of year	2,248	1,530	1,608
Guarantors on a Combined Basis
Condensed Consolidating Financial Information [Line Items]
Net cash provided by operating activities	2,850	3,524	2,884
Cash flows from investing activities:
Maturities of held-to-maturity securities		0	0
Purchases of available-for-sale securities		(99)
Purchases of held-to-maturity securities		0	0
Capital expenditures	(390)	(381)	(301)
Business acquisitions, net of cash acquired	(297)	(1,327)
Other, net	(1)	192	(93)
Net cash used by investing activities	(688)	(1,615)	(394)
Cash flows from financing activities:
Proceeds from fixed-rate notes	0	0
Purchases of common stock	0	0	0
Repayment of fixed-rate notes	0	0	0
Dividends paid	0	0	0
Other, net	(21)	(20)	(1)
Net cash used by financing activities	(21)	(20)	(1)
Net cash used by discontinued operations	0	0	0
Cash sweep/funding by parent	(2,141)	(1,889)	(2,489)
Net 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	378	73	493
Cash flows from investing activities:
Maturities of held-to-maturity securities		107	332
Purchases of available-for-sale securities		0
Purchases of held-to-maturity securities		0	(231)
Capital expenditures	(58)	(71)	(59)
Business acquisitions, net of cash acquired	(26)	0
Other, net	18	(3)	(70)
Net cash used by investing activities	(66)	33	(28)
Cash flows from financing activities:
Proceeds from fixed-rate notes	0	0
Purchases of common stock	0	0	0
Repayment of fixed-rate notes	0	0	0
Dividends paid	0	0	0
Other, net	(2)	(3)	(4)
Net cash used by financing activities	(2)	(3)	(4)
Net cash used by discontinued operations	0	(27)	(2)
Cash sweep/funding by parent	(381)	38	(311)
Net increase in cash and equivalents	(71)	114	148
Cash and equivalents at beginning of year	1,119	1,005	857
Cash and equivalents at end of year	1,048	1,119	1,005
Consolidating Adjustments
Condensed Consolidating Financial Information [Line Items]
Net cash provided by operating activities	0	0	0
Cash flows from investing activities:
Maturities of held-to-maturity securities		0	0
Purchases of available-for-sale securities		0
Purchases of held-to-maturity securities		0	0
Capital expenditures	0	0	0
Business acquisitions, net of cash acquired	0	0
Other, net	0	0	0
Net cash used by investing activities	0	0	0
Cash flows from financing activities:
Proceeds from fixed-rate notes	0	0
Purchases of common stock	0	0	0
Repayment of fixed-rate notes	0	0	0
Dividends paid	0	0	0
Other, net	0	0	0
Net cash used by financing activities	0	0	0
Net cash used by discontinued operations	0	0	0
Cash sweep/funding by parent	0	0	0
Net 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