Subsequent Events - Narrative (Details) - USD ($) $ in Millions		6 Months Ended
	Jul. 09, 2019	Jun. 30, 2019
Subsequent Event [Line Items]
Amount paid to acquire indefinite-lived FCC spectrum licenses		$ 17.0
Amount paid at close to acquire indefinite-lived FCC spectrum licenses		$ 4.0
Remaining lease term (in years)		20 years
Subsequent Event
Subsequent Event [Line Items]
Amount remitted to seller for purchase of indefinite-lived licenses	$ 13.8