Segment Information Gross Profit by Segment and Category (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Gross Profit by Category [Line Items]
Gross Profit	$ 309,425	$ 293,268	$ 946,943	$ 928,747
North America [Member]
Gross Profit by Category [Line Items]
Gross Profit	207,908	201,661	662,705	634,778
International [Member]
Gross Profit by Category [Line Items]
Gross Profit	101,517	91,607	284,238	293,969
Local [Member] | North America [Member]
Gross Profit by Category [Line Items]
Gross Profit	162,914	152,873	511,865	475,703
Local [Member] | International [Member]
Gross Profit by Category [Line Items]
Gross Profit	67,860	59,257	189,357	186,448
Goods [Member] | North America [Member] | Third party and other [Member]
Gross Profit by Category [Line Items]
Gross Profit	3,205	1,509	7,719	5,201
Goods [Member] | North America [Member] | Direct [Member]
Gross Profit by Category [Line Items]
Gross Profit	27,729	30,022	96,141	104,571
Goods [Member] | International [Member] | Third party and other [Member]
Gross Profit by Category [Line Items]
Gross Profit	3,639	5,698	11,800	23,249
Goods [Member] | International [Member] | Direct [Member]
Gross Profit by Category [Line Items]
Gross Profit	21,096	14,274	54,127	50,168
Travel [Member] | North America [Member]
Gross Profit by Category [Line Items]
Gross Profit	14,060	17,257	46,980	49,303
Travel [Member] | International [Member]
Gross Profit by Category [Line Items]
Gross Profit	$ 8,922	$ 12,378	$ 28,954	$ 34,104