Restatement and Revision of Quarterly Condensed Consolidated Financial Statements - Consolidated Statements of Cash Flows Adjustments (Details) - USD ($) $ in Thousands	3 Months Ended								6 Months Ended	9 Months Ended			12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net income (loss)	$ (12,055)	$ (12,737)	$ (9,140)	$ (6,539)	$ (6,876)	$ (15,532)	$ (36,980)	$ (26,576)	$ (15,679)	$ (28,416)	$ (79,088)	$ (155,939)	$ (40,471)	$ (85,964)	$ (157,957)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation expense and amortization of operating leases' right of use assets				7,711					15,447	21,675	16,226	8,107	29,773	23,644	10,745
Deferred income taxes				327					53	569	(2,118)	78,660	624	(1,816)	79,954
Change in operating assets and liabilities, net of effects of acquisitions and divestiture:
Unbilled receivables				39,465					79,842	122,498	111,453	118,872	156,202	147,868	145,164
Prepaid expenses and other assets				1,855					1,726	2,114	4,544	(4,623)	2,057	4,076	(4,978)
Net cash provided by operating activities				37,258					99,273	143,392	93,124	51,170	185,459	128,535	86,223
Cash flows from investing activities:
Proceeds from sale of assets held for sale				0					0	0	0	4,648	0	0	4,648
Net cash used in investing activities				42,217					(91,380)	(146,074)	(110,909)	(12,961)	(90,394)	(141,474)	(67,142)
As originally reported
Cash flows from operating activities:
Net income (loss)		(12,779)	(10,781)	(7,983)		(17,331)			(18,764)	(31,543)	(80,887)		(43,609)	(90,419)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation expense and amortization of operating leases' right of use assets				7,300					14,625	20,853			28,951	23,507
Deferred income taxes									102	618			685
Change in operating assets and liabilities, net of effects of acquisitions and divestiture:
Unbilled receivables				41,321					83,577	126,324	113,264		160,116	151,513
Prepaid expenses and other assets				1,854					1,849	2,188	4,532	(3,729)	2,042	4,064	(4,084)
Net cash provided by operating activities				37,258					99,273	143,392	93,124	52,064	185,459	128,535	87,117
Cash flows from investing activities:
Proceeds from sale of assets held for sale												3,754			3,754
Net cash used in investing activities												(13,855)			(68,036)
Adjustments
Cash flows from operating activities:
Net income (loss)		$ 42	$ 1,641	1,444		$ 1,799			3,085	3,127	1,799		3,138	4,455
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation expense and amortization of operating leases' right of use assets				411					822	822			822	137
Deferred income taxes									(49)	(49)			(61)
Change in operating assets and liabilities, net of effects of acquisitions and divestiture:
Unbilled receivables				(1,856)					(3,735)	(3,826)	(1,811)		(3,914)	(3,645)
Prepaid expenses and other assets				1					(123)	(74)	12	(894)	15	12	(894)
Net cash provided by operating activities				$ 0					$ 0	$ 0	$ 0	(894)	$ 0	$ 0	(894)
Cash flows from investing activities:
Proceeds from sale of assets held for sale												894			894
Net cash used in investing activities												$ 894			$ 894