Segments - Segments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Segment Reporting Information [Line Items]
Service revenue, net	$ 282,256	$ 363,911	$ 649,547	$ 731,726
Service expense	196,106	345,948	528,767	686,446
General and administrative expense	31,199	16,860	51,994	36,262
Depreciation and amortization	6,108	4,353	9,898	8,827
Operating income (loss)	48,843	(3,250)	58,888	191
Equity in net gain of investee	4,425	(1,315)	1,875	(2,971)
Equity investment	131,974		131,974		$ 130,869
Total assets (continuing operations)	654,334		654,334		$ 597,381
NET Services
Segment Reporting Information [Line Items]
Service revenue, net	282,256	363,911	649,547	731,726
Continuing operations
Segment Reporting Information [Line Items]
Service revenue, net	282,256	363,911	649,547	731,726
Service expense	196,106	345,948	528,767	686,446
General and administrative expense	31,199	16,860	51,994	36,262
Depreciation and amortization	6,108	4,353	9,898	8,827
Operating income (loss)	48,843	(3,250)	58,888	191
Equity in net gain of investee	4,425	(1,315)	1,875	(2,971)
Equity investment	131,974	157,948	131,974	157,948
Total assets (continuing operations)	654,245	601,651	654,245	601,651
Continuing operations | NET Services
Segment Reporting Information [Line Items]
Service revenue, net	282,256	363,911	649,547	731,726
Service expense	196,106	345,948	528,767	686,446
General and administrative expense	31,199	16,860	51,994	36,262
Depreciation and amortization	6,108	4,353	9,898	8,827
Operating income (loss)	48,843	(3,250)	58,888	191
Equity in net gain of investee	0	0	0	0
Equity investment	0	0	0	0
Total assets (continuing operations)	522,271	443,703	522,271	443,703
Continuing operations | Matrix Investment
Segment Reporting Information [Line Items]
Service revenue, net	0	0	0	0
Service expense	0	0	0	0
General and administrative expense	0	0	0	0
Depreciation and amortization	0	0	0	0
Operating income (loss)	0	0	0	0
Equity in net gain of investee	4,425	(1,315)	1,875	(2,971)
Equity investment	131,974	157,948	131,974	157,948
Total assets (continuing operations)	$ 131,974	$ 157,948	$ 131,974	$ 157,948