Goodwill and intangible assets - Other Amortizable Intangible (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016
Changes in other amortizable intangible assets
Balance at the beginning of the period			$ 61,499
Additions			39
Amortization	$ (3,400)	$ (3,300)	(10,073)	$ (10,100)
Net balance at the end of the period	51,465		51,465
Future estimated amortization expense
2016					$ 3,357
2017					13,262
2018					13,196
2019					8,432
2020 and thereafter					13,218
Total	51,465		$ 61,499		51,465
Weighted Average
Future estimated amortization expense
Remaining amortization period			4 years 4 months 24 days
Affiliate relationships
Changes in other amortizable intangible assets
Balance at the beginning of the period			$ 56,766
Amortization			(9,224)
Net balance at the end of the period	47,542		47,542
Future estimated amortization expense
Total	47,542		56,766		47,542
Advertiser relationships
Changes in other amortizable intangible assets
Balance at the beginning of the period			2,344
Amortization			(414)
Net balance at the end of the period	1,930		1,930
Future estimated amortization expense
Total	1,930		2,344		1,930
Non-compete agreements
Changes in other amortizable intangible assets
Balance at the beginning of the period			2,333
Amortization			(412)
Net balance at the end of the period	1,921		1,921
Future estimated amortization expense
Total	1,921		2,333		1,921
Other intangibles
Changes in other amortizable intangible assets
Balance at the beginning of the period			56
Additions			39
Amortization			(23)
Net balance at the end of the period	72		72
Future estimated amortization expense
Total	$ 72		$ 56		$ 72