Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Sales Revenue, Services, Net									$ (1,266,452)	$ (1,206,441)	$ (1,250,149)
Restructuring charges		$ 11,500	$ 4,600	$ 2,700	$ 12,100	$ 1,200	$ 15,700	$ 11,500	18,828	40,438	28,464
Total revenue	$ 873,166	$ 634,466	$ 662,619	$ 673,626	$ 904,865	$ 686,555	$ 723,760	$ 698,435	2,843,877	3,013,615	2,954,816
Sales Revenue, Goods, Net									1,577,425	1,807,174	1,704,667
UNITED STATES
Segment Reporting Information [Line Items]
Total revenue									1,884,700	2,120,300	2,022,500
North America [Member]
Segment Reporting Information [Line Items]
Sales Revenue, Services, Net									(1,914,168)	(2,151,769)	(2,047,742)
International [Member]
Segment Reporting Information [Line Items]
Total revenue									929,709	861,846	907,074
Local [Member] | North America [Member]
Segment Reporting Information [Line Items]
Sales Revenue, Services, Net									(825,579)	(762,314)	(701,312)
Local [Member] | International [Member]
Segment Reporting Information [Line Items]
Sales Revenue, Services, Net									(281,466)	(270,045)	(335,112)
Travel [Member] | North America [Member]
Segment Reporting Information [Line Items]
Sales Revenue, Services, Net									(78,495)	(82,577)	(81,731)
Travel [Member] | International [Member]
Segment Reporting Information [Line Items]
Sales Revenue, Services, Net									(43,786)	(49,756)	(59,482)
Third party and other [Member] | Goods [Member] | North America [Member]
Segment Reporting Information [Line Items]
Sales Revenue, Services, Net									(16,768)	(9,068)	(7,151)
Third party and other [Member] | Goods [Member] | International [Member]
Segment Reporting Information [Line Items]
Sales Revenue, Services, Net									(20,358)	(32,681)	(65,361)
Direct [Member] | Goods [Member] | North America [Member]
Segment Reporting Information [Line Items]
Sales Revenue, Goods, Net									993,326	1,297,810	1,257,548
Direct [Member] | Goods [Member] | International [Member]
Segment Reporting Information [Line Items]
Sales Revenue, Goods, Net									$ 584,099	$ 509,364	$ 447,119