Goodwill and intangible assets (Details 3) (USD $) In Thousands, unless otherwise specified				12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Venue contracts	Dec. 31, 2012 Venue contracts	Dec. 31, 2013 Non-compete agreements	Dec. 31, 2013 Technology	Dec. 31, 2012 Technology	Dec. 31, 2013 Advertiser relationships	Dec. 31, 2012 Advertiser relationships	Dec. 31, 2013 Patents, trademarks and other	Dec. 31, 2012 Patents, trademarks and other
Intangible assets
Weighted Average Life				10 years	11 years	5 years	6 years	5 years	5 years	5 years	6 years	5 years
Historical Cost	$ 43,974	$ 28,905		$ 36,356	$ 26,886	$ 3,840	$ 2,300	$ 1,110	$ 70	$ 70	$ 1,408	$ 839
Accumulated Amortization	(20,561)	(18,311)		(19,314)	(17,783)	(224)	(441)	(93)	(20)	(6)	(562)	(429)
Net Book Value	23,413	10,594	9,846	17,042	9,103	3,616	1,859	1,017	50	64	846	410
Amortization expense for fiscal years 2014 through 2018 and thereafter
2014	3,681
2015	3,525
2016	3,451
2017	3,218
2018	2,370
Thereafter	7,168
Net Book Value	$ 23,413	$ 10,594	$ 9,846	$ 17,042	$ 9,103	$ 3,616	$ 1,859	$ 1,017	$ 50	$ 64	$ 846	$ 410