Schedule of Cash Flow Statement Information (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating activities:
Net cash provided by operating activities from continuing operations	$ 1,237,182	$ 825,729	$ 605,387
Investing activities:
Capital expenditures, including internal-use software and website development	(235,697)	(207,837)	(136,376)
Purchases of investments	(1,873,519)	(1,723,350)	(970,339)
Sales and maturities of investments	1,955,955	1,507,240	366,036
Acquisitions, net of cash acquired	(199,360)	(35,221)	(16,019)
Other, net	(15,204)	(39,513)	(3,668)
Net cash used in investing activities from continuing operations	(367,825)	(463,460)	(744,347)
Financing activities:
Proceeds from issuance of long-term debt, net of issuance costs			742,470
Treasury stock activity	(417,571)	(294,027)	(501,993)
Payment of dividends to stockholders	(130,423)	(76,550)	(79,076)
Proceeds from exercise of equity awards	241,193	34,489	50,615
Purchase of additional interests in controlled subsidiaries, net	(2,015)	(22,485)	(77,929)
Other, net	34,014	39,568	44,388
Net cash provided by (used in) financing activities from continuing operations	(272,787)	(353,494)	127,860
Net cash provided by (used in) continuing operations	596,570	8,775	(11,100)
Net cash provided by discontinued operations	(7,607)	76,903	40,999
Effect of exchange rate changes on cash and cash equivalents	15,064	(17,743)	(19,880)
Net increase (decrease) in cash and cash equivalents	604,027	67,935	10,019
Cash and cash equivalents at beginning of year	689,134	621,199	611,180
Cash and cash equivalents at end of year	1,293,161	689,134	621,199
Parent
Financing activities:
Proceeds from issuance of long-term debt, net of issuance costs			742,470
Treasury stock activity	(417,571)	(294,027)	(501,993)
Payment of dividends to stockholders	(130,423)	(76,550)	(79,076)
Proceeds from exercise of equity awards	238,001
Transfers (to) from related parties	268,893	333,303	(219,556)
Other, net	41,100	37,274	58,155
Guarantor Subsidiaries
Operating activities:
Net cash provided by operating activities from continuing operations	1,008,600	527,448	378,370
Investing activities:
Capital expenditures, including internal-use software and website development	(191,423)	(179,159)	(121,687)
Purchases of investments	(1,518,142)	(1,425,578)	(846,344)
Sales and maturities of investments	1,628,365	1,359,439	282,450
Other, net	(12,954)	(6,190)	14,938
Net cash used in investing activities from continuing operations	(94,154)	(251,488)	(670,643)
Financing activities:
Transfers (to) from related parties	(268,893)	(333,303)	219,556
Other, net	(2,292)	(4,285)	(12,959)
Net cash provided by (used in) financing activities from continuing operations	(271,185)	(337,588)	206,597
Net cash provided by (used in) continuing operations	643,261	(61,628)	(85,676)
Net cash provided by discontinued operations	(7,607)	76,903	40,999
Effect of exchange rate changes on cash and cash equivalents	14,250	(19,539)	(13,958)
Net increase (decrease) in cash and cash equivalents	649,904	(4,264)	(58,635)
Cash and cash equivalents at beginning of year	357,252	361,516	420,151
Cash and cash equivalents at end of year	1,007,156	357,252	361,516
Non-Guarantor Subsidiaries
Operating activities:
Net cash provided by operating activities from continuing operations	228,582	298,281	227,017
Investing activities:
Capital expenditures, including internal-use software and website development	(44,274)	(28,678)	(14,689)
Purchases of investments	(355,377)	(297,772)	(123,995)
Sales and maturities of investments	327,590	147,801	83,586
Acquisitions, net of cash acquired	(199,360)
Other, net	(2,250)	(33,323)	(18,606)
Net cash used in investing activities from continuing operations	(273,671)	(211,972)	(73,704)
Financing activities:
Proceeds from exercise of equity awards	3,192
Purchase of additional interests in controlled subsidiaries, net		(22,485)	(77,929)
Other, net	(4,794)	6,579	(808)
Net cash provided by (used in) financing activities from continuing operations	(1,602)	(15,906)	(78,737)
Net cash provided by (used in) continuing operations	(46,691)	70,403	74,576
Effect of exchange rate changes on cash and cash equivalents	814	1,796	(5,922)
Net increase (decrease) in cash and cash equivalents	(45,877)	72,199	68,654
Cash and cash equivalents at beginning of year	331,882	259,683	191,029
Cash and cash equivalents at end of year	$ 286,005	$ 331,882	$ 259,683