Intangibles - Amortizable Intangible Assets Other Than Goodwill (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Noncompetition and other agreements	$ 131,360	$ 429,140
Lease agreements	7,584	7,623
Indefinite-lived assets	59,885	33,255
Other	583	583
Intangible assets, gross (excluding goodwill)	199,412	470,601
Less accumulated amortization	(80,566)	(356,774)
Total intangible assets	$ 118,846	$ 113,827