Restatement of Previously Issued Audited and Unaudited Consolidated Financial Statements - Impact of Restatement on Statements of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended							6 Months Ended	9 Months Ended	12 Months Ended
	Sep. 27, 2020	Jun. 28, 2020	Mar. 29, 2020	Dec. 31, 2019	Sep. 29, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 28, 2020	Sep. 27, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating activities
Net income (loss)	$ 15,731	$ (2,681)	$ 26,150	$ (16,664)	$ (31,625)	$ 3,388	$ (5,160)	$ 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
Inventories, net			1,342					2,415	2,291
Prepaid expenses and other current assets			(2,921)					(3,256)
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	138,469	99,790	68,035				$ 51,097	68,035	68,035	68,035	51,097	93,582
Cash and cash equivalents at end of period	145,446	138,469	99,790	68,035				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
Previously Reported
Operating activities
Net income (loss)	10,731	16,786	(4,777)					12,009	22,739	13,826
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
Amortization of intangible assets			8,047					16,094	24,141	34,154
Amortization of debt issuance cost			6,063					7,821	9,560	6,690
Loss on extinguishment of debt									8,018	16,528
Stock-based compensation								3,700	(3,533)	12,943
Net undistributed (loss) income from unconsolidated ventures			(663)					(1,739)	(11,229)	(6,504)
Deferred income taxes, net			(9,081)					(13,295)	0	(19,278)
Change in fair value of Warrant liability			0					0	382	0
Other non-cash activities, net			270					404		383
Changes in operating assets and liabilities, net of acquisitions:
Accounts receivable, net			20,869					9,607	(3,477)	(54,345)
Accounts payable			(2,417)					(17,547)	15,852	(4,529)
Accrued expenses			(3,779)					6,358	765	9,529
Customer advances and billings in excess of costs			18,223					19,282	8,923	48,618
Salaries, benefits and payroll taxes			(21,307)					4,310	10,975	554
Inventories, net			1,342					2,415	2,291
Prepaid expenses and other current assets			(2,921)					(3,256)
Prepaid expenses and other current assets									(4,409)	(5,862)
Other current and noncurrent liabilities			(4,545)					(5,101)	71	39,215
Investments			750					1,701	2,793	6,538
Other noncurrent assets			4,729					11,600	5,903	(4,141)
Accrued taxes			(2,473)					(3,847)	(4,904)	(2,941)
Net cash provided by (used in) operating activities			10,913					55,588	92,124	100,862
Investing activities
Expenditures for property and equipment			(404)					(1,597)	(2,628)	(3,835)
Acquisition of Metis Solutions Corporation, net of acquired cash										(90,271)
Acquisition of Centra Technology Inc, net of acquired cash										(222,124)
Other investing activities, net								37	(72)	17
Net cash used in investing activities			(404)					(1,560)	(2,700)	(316,213)
Financing activities
Net contributions from noncontrolling interests			150					1,950	2,095	2,095
Borrowings on long-term debt			60,000					60,468	60,734	961,030
Repayments on short-term debt										0
Repayments on long-term debt			(196,544)					(204,464)	(212,184)	(843,131)
Payment of debt issuance costs			(964)					(964)	(964)	(26,646)
Recapitalization from merger with Gores III			605,708					605,713	605,713	605,713
Payment of underwriting and transaction costs			(27,268)					(27,267)	(27,267)	(27,267)
Distribution to selling stockholders			(419,548)					(419,548)	(439,719)	(439,719)
Other financing activities, net								(292)	(292)	(292)
Net cash provided by (used in) financing activities			21,534					15,596	(11,884)	231,783
Effect of exchange rate changes on cash and cash equivalents			(288)					810	(129)	1,441
Net increase (decrease) in cash and cash equivalents			31,755					70,434	77,411	17,873
Cash and cash equivalents at beginning of period	138,469	99,790	68,035					68,035	68,035	68,035
Cash and cash equivalents at end of period	145,446	138,469	99,790	68,035				138,469	145,446	85,908	68,035
Supplemental cash flow information
Cash paid for interest			10,900					23,278	35,085	45,247
Cash paid for taxes			1,523					2,796	5,304	10,936
Restatement Adjustment
Operating activities
Net income (loss)	5,000	(19,467)	30,927					11,460	16,460	13,460
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation of property and equipment			0					0	0	0
Amortization of intangible assets			0					0	0	0
Amortization of debt issuance cost			0					0	0	0
Loss on extinguishment of debt									0	0
Stock-based compensation								0	0	0
Net undistributed (loss) income from unconsolidated ventures			0					0	(815)	0
Deferred income taxes, net			(815)					(815)	(19,132)	(815)
Change in fair value of Warrant liability			(33,599)					(14,132)	0	(16,132)
Other non-cash activities, net			0					0		0
Changes in operating assets and liabilities, net of acquisitions:
Accounts receivable, net			0					0	0	0
Accounts payable			0					0	0	0
Accrued expenses			3,487					3,487	3,487	3,487
Customer advances and billings in excess of costs			0					0	0	0
Salaries, benefits and payroll taxes			0					0	0	0
Inventories, net			0					0	0
Prepaid expenses and other current assets			0					0
Prepaid expenses and other current assets									0	0
Other current and noncurrent liabilities			0					0	0	0
Investments			0					0	0	0
Other noncurrent assets			0					0	0	0
Accrued taxes			0					0	0	0
Net cash provided by (used in) operating activities			0					0	0	0
Investing activities
Expenditures for property and equipment			0					0	0	0
Acquisition of Metis Solutions Corporation, net of acquired cash										0
Acquisition of Centra Technology Inc, net of acquired cash										0
Other investing activities, net								0	0	0
Net cash used in investing activities			0					0	0	0
Financing activities
Net contributions from noncontrolling interests			0					0	0	0
Borrowings on long-term debt			0					0	0	0
Repayments on short-term debt										0
Repayments on long-term debt			0					0	0	0
Payment of debt issuance costs			0					0	0	0
Recapitalization from merger with Gores III			0					0	0	0
Payment of underwriting and transaction costs			0					0	0	0
Distribution to selling stockholders			0					0	0	0
Other financing activities, net								0	0	0
Net cash provided by (used in) financing activities			0					0	0	0
Effect of exchange rate changes on cash and cash equivalents			0					0	0	0
Net increase (decrease) in cash and cash equivalents			0					0	0	0
Cash and cash equivalents at beginning of period	0	0	0					0	0	0
Cash and cash equivalents at end of period	$ 0	$ 0	0	$ 0				0	0	0	$ 0
Supplemental cash flow information
Cash paid for interest			0					0	0	0
Cash paid for taxes			$ 0					$ 0	$ 0	$ 0