Goodwill and intangible assets - Other Amortizable Intangible (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019
Changes in other amortizable intangible assets
Net balance at the beginning of the period			$ 22,400
Amortization of Intangible Assets	$ 1,800	$ 3,300	5,089	$ 6,600
Net balance at the end of the period	17,311		17,311
Future estimated amortization expense
Remainder of 2019					$ 3,508
2020					6,170
2021					5,857
2022					1,528
2023 and thereafter					248
Total	17,311		$ 22,400		17,311
Weighted Average
Changes in other amortizable intangible assets
Remaining amortization period			2 years 9 months 18 days
Affiliate relationships
Changes in other amortizable intangible assets
Net balance at the beginning of the period			$ 20,273
Amortization of Intangible Assets			4,456
Net balance at the end of the period	15,817		15,817
Future estimated amortization expense
Total	15,817		20,273		15,817
Advertiser relationships
Changes in other amortizable intangible assets
Net balance at the beginning of the period			690
Amortization of Intangible Assets			276
Net balance at the end of the period	414		414
Future estimated amortization expense
Total	414		690		414
Non-compete agreement
Changes in other amortizable intangible assets
Net balance at the beginning of the period			686
Amortization of Intangible Assets			274
Net balance at the end of the period	412		412
Future estimated amortization expense
Total	412		686		412
Other intangibles
Changes in other amortizable intangible assets
Net balance at the beginning of the period			144
Amortization of Intangible Assets			38
Net balance at the end of the period	106		106
Future estimated amortization expense
Total	106		144		106
Programming contracts
Changes in other amortizable intangible assets
Net balance at the beginning of the period			607
Amortization of Intangible Assets			45
Net balance at the end of the period	562		562
Future estimated amortization expense
Total	$ 562		$ 607		$ 562