Acquisitions - Additional Information (Detail) (Trivago) In Millions, unless otherwise specified	Dec. 31, 2012 EUR (€)	Dec. 31, 2012 Third Anniversary	Dec. 31, 2012 Fifth Anniversary	Jan. 31, 2013 January 31, 2013 exchange rate USD ($)
Business Acquisition [Line Items]
Definitive agreement to acquire equity position, percentage	63.00%
Definitive agreement to acquire equity position, total consideration	€ 477			$ 647
Definitive agreement to acquire equity position, cash consideration	434
Definitive agreement to acquire equity position, common stock consideration	€ 43
Definitive agreement to acquire fully diluted basis, percentage	61.60%
Minority shareholders right to sell on remaining shares of trivago		50.00%	100.00%