Goodwill and intangible assets - Other Amortizable Intangible (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016
Changes in other amortizable intangible assets
Balance at the beginning of the period			$ 61,499
Additions			23
Amortization	$ 3,400	$ 3,300	(6,714)	$ 6,800
Net balance at the end of the period	54,808		54,808
Future estimated amortization expense
2016					$ 6,714
2017					13,257
2018					13,187
2019					8,432
2020 and thereafter					13,218
Total	54,808		$ 61,499		54,808
Weighted Average
Future estimated amortization expense
Remaining amortization period			4 years 7 months 6 days
Affiliate relationships
Changes in other amortizable intangible assets
Balance at the beginning of the period			$ 56,766
Amortization			(6,149)
Net balance at the end of the period	50,617		50,617
Future estimated amortization expense
Total	50,617		56,766		50,617
Advertiser relationships
Changes in other amortizable intangible assets
Balance at the beginning of the period			2,344
Amortization			(276)
Net balance at the end of the period	2,068		2,068
Future estimated amortization expense
Total	2,068		2,344		2,068
Non-compete agreements
Changes in other amortizable intangible assets
Balance at the beginning of the period			2,333
Amortization			(274)
Net balance at the end of the period	2,059		2,059
Future estimated amortization expense
Total	2,059		2,333		2,059
Other intangibles
Changes in other amortizable intangible assets
Balance at the beginning of the period			56
Additions			23
Amortization			(15)
Net balance at the end of the period	64		64
Future estimated amortization expense
Total	$ 64		$ 56		$ 64