Unaudited Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Service revenue, net	$ 320,619	$ 393,385	$ 970,166	$ 1,125,111
Operating expenses:
Service expense	235,543	356,271	764,310	1,042,717
General and administrative expense	34,441	15,979	86,435	52,241
Depreciation and amortization	7,301	4,148	17,199	12,976
Total operating expenses	277,285	376,398	867,944	1,107,934
Operating income	43,334	16,987	102,222	17,177
Other expenses (income):
Interest expense, net	379	188	2,118	793
Other income	0	(66)	0	(199)
Equity in net (income) loss of investee	(10,325)	3,188	(12,200)	6,159
Income from continuing operations before income taxes	53,280	13,677	112,304	10,424
Provision for income taxes	14,360	5,097	19,785	3,940
Income from continuing operations, net of tax	38,920	8,580	92,519	6,484
(Loss) income from discontinued operations, net of tax	(115)	(426)	(618)	540
Net income	38,805	8,154	91,901	7,024
Net income available to common stockholders	$ 35,346	$ 6,104	$ 34,563	$ 3,230
Basic earnings (loss) per common share:
Continuing operations (in dollars per share)	$ 2.53	$ 0.50	$ 2.63	$ 0.21
Discontinued operations (in dollars per share)	(0.01)	(0.03)	(0.05)	0.04
Basic earnings per common share (in dollars per share)	2.52	0.47	2.58	0.25
Diluted earnings (loss) per common share:
Continuing operations (in dollars per share)	2.51	0.50	2.62	0.21
Discontinued operations (in dollars per share)	(0.01)	(0.03)	(0.05)	0.04
Diluted (loss) earnings per common share (in dollars per share)	$ 2.50	$ 0.47	$ 2.57	$ 0.25
Weighted-average number of common shares outstanding:
Basic (in shares)	14,026,039	12,993,934	13,367,605	12,956,222
Diluted (in shares)	14,133,904	13,004,449	13,415,344	12,977,598