Intangibles and Goodwill - Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Intangible assets:
Goodwill	$ 309,589		$ 309,589		$ 309,589
Summary of amortizable intangible assets:
Cost	179,418		179,418		179,418
Accumulated Amortization	(89,939)		(89,939)		(81,656)
Net	89,479		89,479		97,762
Amortization expense	2,700	$ 2,800	8,300	$ 9,000
Estimated amortization expense for the next five years and thereafter:
Remainder of 2020	2,691		2,691
2021	10,362		10,362
2022	10,005		10,005
2023	9,501		9,501
2024	8,897		8,897
Thereafter	48,023		48,023
Net	89,479		89,479		97,762
Customer relationships
Summary of amortizable intangible assets:
Cost	150,239		150,239		150,239
Accumulated Amortization	(74,352)		(74,352)		(67,317)
Net	75,887		$ 75,887		82,922
Weighted-average, useful life			14 years 9 months 18 days
Estimated amortization expense for the next five years and thereafter:
Net	75,887		$ 75,887		82,922
Carrier relationships
Summary of amortizable intangible assets:
Cost	18,300		18,300		18,300
Accumulated Amortization	(5,741)		(5,741)		(4,934)
Net	12,559		$ 12,559		13,366
Weighted-average, useful life			17 years
Estimated amortization expense for the next five years and thereafter:
Net	12,559		$ 12,559		13,366
Non-compete agreements
Summary of amortizable intangible assets:
Cost	5,239		5,239		5,239
Accumulated Amortization	(4,206)		(4,206)		(3,765)
Net	1,033		$ 1,033		1,474
Weighted-average, useful life			6 years 8 months 12 days
Estimated amortization expense for the next five years and thereafter:
Net	1,033		$ 1,033		1,474
Trade names
Summary of amortizable intangible assets:
Cost	5,640		5,640		5,640
Accumulated Amortization	(5,640)		(5,640)		(5,640)
Net	0		$ 0		0
Weighted-average, useful life			4 years
Estimated amortization expense for the next five years and thereafter:
Net	$ 0		$ 0		$ 0