Schedule of Cash Flow Statement Information (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Operating activities:
Net cash provided by operating activities from continuing operations	$ 1,453,908	$ 1,018,698
Investing activities:
Capital expenditures, including internal-use software and website development	(176,980)	(157,867)
Purchases of investments	(1,530,749)	(1,179,555)
Sales and maturities of investments	1,244,065	1,046,395
Acquisitions, net of cash acquired	(198,398)	(8,076)
Other, net	(10,714)	(15,154)
Net cash used in investing activities from continuing operations	(672,776)	(306,181)
Financing activities:
Treasury stock activity	(366,037)	(208,693)
Payment of dividends to stockholders	(42,470)	(57,732)
Proceeds from exercise of equity awards	232,658	23,127
Sales of additional interests in controlled subsidiaries, net	(2,015)	70,626
Other, net	21,922	26,539
Net cash provided by (used in) financing activities from continuing operations	(153,927)	(169,260)
Net cash provided by (used in) continuing operations	627,205	543,257
Net cash provided by discontinued operations	(7,607)	114,412
Effect of exchange rate changes on cash and cash equivalents	5,996	(13,279)
Net increase (decrease) in cash and cash equivalents	625,594	644,390
Cash and cash equivalents at beginning of period	689,134	621,199
Cash and cash equivalents at end of period	1,314,728	1,265,589
Parent Company
Financing activities:
Treasury stock activity	(366,037)	(208,693)
Payment of dividends to stockholders	(42,470)	(57,732)
Proceeds from exercise of equity awards	231,073
Transfers (to) from related parties	149,001	241,554
Other, net	28,433	24,871
Guarantor Subsidiaries
Operating activities:
Net cash provided by operating activities from continuing operations	1,270,214	924,286
Investing activities:
Capital expenditures, including internal-use software and website development	(143,051)	(140,897)
Purchases of investments	(1,265,212)	(1,111,613)
Sales and maturities of investments	992,292	973,476
Other, net	(8,511)	(8,117)
Net cash used in investing activities from continuing operations	(424,482)	(287,151)
Financing activities:
Transfers (to) from related parties	(149,001)	(241,554)
Other, net	(2,746)	(3,888)
Net cash provided by (used in) financing activities from continuing operations	(151,747)	(245,442)
Net cash provided by (used in) continuing operations	693,985	391,693
Net cash provided by discontinued operations	(7,607)	114,412
Effect of exchange rate changes on cash and cash equivalents	5,863	(14,950)
Net increase (decrease) in cash and cash equivalents	692,241	491,155
Cash and cash equivalents at beginning of period	357,252	361,516
Cash and cash equivalents at end of period	1,049,493	852,673
Non-Guarantor Subsidiaries
Operating activities:
Net cash provided by operating activities from continuing operations	183,694	94,412
Investing activities:
Capital expenditures, including internal-use software and website development	(33,929)	(16,970)
Purchases of investments	(265,537)	(67,942)
Sales and maturities of investments	251,773	72,919
Acquisitions, net of cash acquired	(198,398)
Other, net	(2,203)	(7,037)
Net cash used in investing activities from continuing operations	(248,294)	(19,030)
Financing activities:
Proceeds from exercise of equity awards	1,585
Sales of additional interests in controlled subsidiaries, net		70,626
Other, net	(3,765)	5,556
Net cash provided by (used in) financing activities from continuing operations	(2,180)	76,182
Net cash provided by (used in) continuing operations	(66,780)	151,564
Effect of exchange rate changes on cash and cash equivalents	133	1,671
Net increase (decrease) in cash and cash equivalents	(66,647)	153,235
Cash and cash equivalents at beginning of period	331,882	259,683
Cash and cash equivalents at end of period	$ 265,235	$ 412,917