Goodwill and intangible assets - Other Amortizable Intangible (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2019
Changes in other amortizable intangible assets
Net balance at the beginning of the period	$ 22,400
Amortization	(3,334)
Net balance at the end of the period	19,066
Future estimated amortization expense
Remainder of 2019		$ 5,263
2020		6,170
2021		5,857
2022		1,528
2023 and thereafter		248
Total	$ 22,400	19,066
Weighted Average
Changes in other amortizable intangible assets
Remaining amortization period	3 years
Affiliate relationships
Changes in other amortizable intangible assets
Net balance at the beginning of the period	$ 20,273
Amortization	(3,018)
Net balance at the end of the period	17,255
Future estimated amortization expense
Total	20,273	17,255
Advertiser relationships
Changes in other amortizable intangible assets
Net balance at the beginning of the period	690
Amortization	(138)
Net balance at the end of the period	552
Future estimated amortization expense
Total	690	552
Non-compete agreement
Changes in other amortizable intangible assets
Net balance at the beginning of the period	686
Amortization	(137)
Net balance at the end of the period	549
Future estimated amortization expense
Total	686	549
Other intangibles
Changes in other amortizable intangible assets
Net balance at the beginning of the period	144
Amortization	(19)
Net balance at the end of the period	125
Future estimated amortization expense
Total	144	125
Programming contracts
Changes in other amortizable intangible assets
Net balance at the beginning of the period	607
Amortization	(22)
Net balance at the end of the period	585
Future estimated amortization expense
Total	$ 607	$ 585