Acquisitions, Disposals and Other Transactions - Additional Information (Detail) $ / shares in Units, £ in Millions, $ in Millions			1 Months Ended			3 Months Ended		6 Months Ended
	Sep. 30, 2015 USD ($)	Sep. 30, 2015 GBP (£)	Jul. 31, 2015 USD ($)	Nov. 30, 2014 USD ($) $ / shares	Aug. 31, 2014 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 GBP (£)
REA Group [Member]
Schedule Of Business Acquisitions And Divestitures [Line Items]
Interest acquired						20.00%		20.00%
Company ownership percentage						61.60%
Harlequin Enterprises Limited [Member]
Schedule Of Business Acquisitions And Divestitures [Line Items]
Business acquisition, cost of acquired entity					$ 414
Business acquisition purchase price allocation, amortizable intangible assets					$ 60
Finite lived intangible assets, weighted average useful life					5 years
Business acquisition purchase price allocation, goodwill amount					$ 185
Business acquisition purchase price allocation, cash					19
Business acquisition purchase price allocation, net tangible assets					115
Business acquisition purchase price allocation, net intangible assets					165
Business acquisition purchase price allocation, non-amortizable intangible assets					105
Business acquisition purchase price allocation, deferred tax liability					$ 35
Move Inc [Member]
Schedule Of Business Acquisitions And Divestitures [Line Items]
Business acquisition, cost of acquired entity				$ 892
Business acquisition purchase price allocation, cash				108
Business acquisition purchase price allocation, net intangible assets				$ 216
Shares purchase price | $ / shares				$ 21.00
Business acquisition, cost of acquired entity, cash paid				$ 864
Fair value of assumed outstanding equity-based compensation awards				67
Assumed equity-based compensation awards - pre-combination services				28
Consideration transferred for future services				$ 39
Business combination, weighted average remaining service period				2 years 6 months
Business acquisition, cash paid for outstanding indebtedness				$ 129
Move Inc [Member] | U.S. Federal [Member]
Schedule Of Business Acquisitions And Divestitures [Line Items]
Net operating loss carryforwards				947
Net operating loss carryforwards, tax-effected				332
Valuation allowances and unrecognized tax benefits				484
Valuation allowances and unrecognized tax benefits, tax-effected				170
Expected net operating loss carryforwards to be utilized				463
Net deferred tax asset				$ 162
Increase in expected net operating loss carryforwards							$ 167
Increase in expected net operating loss carryforwards tax-effected							58
Expected net operating loss carryforwards						$ 630		$ 630
Expected net operating loss carryforwards tax-effected						220		220
Move Inc [Member] | Trademarks [Member]
Schedule Of Business Acquisitions And Divestitures [Line Items]
Business acquisition purchase price allocation, non-amortizable intangible assets						116		116
Move Inc [Member] | Customer Relationships Other Trade Names And Listing Service Agreements [Member]
Schedule Of Business Acquisitions And Divestitures [Line Items]
Business acquisition purchase price allocation, amortizable intangible assets						100		$ 100
Finite lived intangible assets, weighted average useful life								15 years
Move Inc [Member] | Technology-Based Intangible Assets [Member]
Schedule Of Business Acquisitions And Divestitures [Line Items]
Business acquisition purchase price allocation, amortizable intangible assets						$ 39		$ 39
Finite lived intangible assets, weighted average useful life								4 years
Unruly Holdings Limited [Member]
Schedule Of Business Acquisitions And Divestitures [Line Items]
Business acquisition, cost of acquired entity	$ 90	£ 60
Future cash consideration related to contingent payments	86						86		£ 56
Future consideration related to contingent payments	40						40
Business acquisition purchase price allocation, goodwill amount	67
Unruly Holdings Limited [Member] | Acquired Technology [Member]
Schedule Of Business Acquisitions And Divestitures [Line Items]
Business acquisition purchase price allocation, amortizable intangible assets	$ 42						42
Finite lived intangible assets, weighted average useful life	7 years	7 years
Unruly Holdings Limited [Member] | Customer Relationships and Trade Names [Member]
Schedule Of Business Acquisitions And Divestitures [Line Items]
Business acquisition purchase price allocation, amortizable intangible assets	$ 25						$ 25
Finite lived intangible assets, weighted average useful life	6 years	6 years
Checkout 51 [Member]
Schedule Of Business Acquisitions And Divestitures [Line Items]
Business acquisition, cost of acquired entity			$ 13
Future cash consideration related to contingent payments			$ 28