Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	9 Months Ended	12 Months Ended
	Mar. 29, 2020	Jun. 28, 2020	Sep. 27, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating activities
Net income (loss)	$ 26,150	$ 23,469	$ 39,199	$ 27,286	$ (50,061)	$ (31,578)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation of property and equipment	2,583	5,072	7,263	9,484	12,875	14,459
Amortization of intangible assets	8,047	16,094	24,141	34,154	33,205	33,817
Amortization of debt issuance cost	6,063	7,821	9,560	6,690	8,092	8,382
Loss on extinguishment of debt			8,018	16,528	0	0
Stock-based compensation		3,700	(3,533)	12,943	0	0
Net undistributed (loss) income from unconsolidated ventures	(663)	(1,739)	(12,044)	(6,504)	(2,680)	180
Deferred income taxes, net	(9,896)	(14,110)	(19,132)	(20,093)	(17,247)	(14,801)
Change in fair value of Warrant liability	(33,599)	(14,132)	382	(16,132)	0	0
Other non-cash activities, net	270	404		383	36,942	380
Changes in operating assets and liabilities, net of acquisitions:
Accounts receivable, net	20,869	9,607	(3,477)	(54,345)	74,416	(101,178)
Accounts payable	(2,417)	(17,547)	15,852	(4,529)	618	35,404
Accrued expenses	(292)	9,845	4,252	13,016	(5,629)	12,058
Customer advances and billings in excess of costs	18,223	19,282	8,923	48,618	23,569	(15,004)
Salaries, benefits and payroll taxes	(21,307)	4,310	10,975	554	17,411	7,510
Prepaid expenses and other current assets			(4,409)	(5,862)	3,202	355
Other current and noncurrent liabilities	(4,545)	(5,101)	71	39,215	(25,220)	(8,628)
Investments	750	1,701	2,793	6,538	6,102	12,973
Other noncurrent assets	4,729	11,600	5,903	(4,141)	1,450	(688)
Accrued taxes	(2,473)	(3,847)	(4,904)	(2,941)	(397)	(10,482)
Net cash provided by (used in) operating activities	10,913	55,588	92,124	100,862	116,648	(56,841)
Investing activities
Expenditures for property and equipment	(404)	(1,597)	(2,628)	(3,835)	(9,436)	(5,702)
Acquisition of Metis Solutions Corporation, net of acquired cash				(90,271)	0	0
Acquisition of Centra Technology Inc, net of acquired cash				(222,124)	0	0
Other investing activities, net		37	(72)	17	6,747	(10,849)
Net cash used in investing activities	(404)	(1,560)	(2,700)	(316,213)	(2,689)	(16,551)
Financing activities
Net contributions from noncontrolling interests	150	1,950	2,095	2,095	5,405	0
Borrowings on long-term debt	60,000	60,468	60,734	961,030	267,375	107,099
Repayments on short-term debt				0	0	(1,966)
Repayments on long-term debt	(196,544)	(204,464)	(212,184)	(843,131)	(367,312)	(69,480)
Payment of debt issuance costs	(964)	(964)	(964)	(26,646)	0	0
Recapitalization from merger with Gores III	605,708	605,713	605,713	605,713	0	0
Payment of underwriting and transaction costs	(27,268)	(27,267)	(27,267)	(27,267)	0	0
Distribution to selling stockholders	(419,548)	(419,548)	(439,719)	(439,719)	0	0
Other financing activities, net		(292)	(292)	(292)	(742)	(2,806)
Net cash provided by (used in) financing activities	21,534	15,596	(11,884)	231,783	(95,274)	32,847
Effect of exchange rate changes on cash and cash equivalents	(288)	810	(129)	1,441	(1,747)	(1,940)
Net increase (decrease) in cash and cash equivalents	31,755	70,434	77,411	17,873	16,938	(42,485)
Cash and cash equivalents at beginning of period	68,035	68,035	68,035	68,035	51,097	93,582
Cash and cash equivalents at end of period	99,790	138,469	145,446	85,908	68,035	51,097
Supplemental cash flow information
Cash paid for interest	10,900	23,278	35,085	45,247	78,019	74,579
Cash paid for taxes	$ 1,523	$ 2,796	$ 5,304	$ 10,936	$ 9,552	$ 19,093