Restatement and Revision of Quarterly Condensed Consolidated Financial Statements - Consolidated Balance Sheets (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 136,146	$ 89,475	$ 103,275	$ 175,446	$ 102,176	$ 91,838
Marketable securities	366,503	430,746	382,802	259,999	305,488	246,186
Accounts receivable	27,903	33,025	35,198	44,364	44,039	38,610
Unbilled receivables	138,813	143,514	156,887	172,757	184,366	182,934
Inventories	14,466	14,218	11,554	9,848	10,086	9,854
Assets held for sale		0	0	0		77,203
Prepaids and other current assets	15,881	16,292	18,080	17,042	18,512	9,812
Total current assets	699,712	727,270	707,796	679,456	664,667	656,437
Intangible assets, net	36,487	41,052	45,624	50,208	54,900	35,362
Goodwill	183,222	183,222	183,222	183,465	183,465	164,488		$ 207,178
Property, plant and equipment, net	57,693	59,425	50,858	48,154	45,536	38,571
Operating lease right-of-use assets	28,708	29,961	31,407	34,493	37,020	15,503
Deferred tax assets	4,353	5,249	5,350	4,541	4,574	6,454
Unbilled receivables, long-term	236,699	265,701	294,986	319,494	347,348	378,430
Other assets	4,535	4,671	4,895	5,579	5,931	6,381
Total assets	1,251,409	1,316,551	1,324,138	1,325,390	1,343,441	1,301,626
Current liabilities:
Accounts payable	8,993	13,323	14,016	15,730	9,549	9,429
Accrued salaries and benefits	23,326	15,719	16,170	12,411	20,291	13,294
Deferred revenue	10,198	14,950	10,841	10,121	11,947	9,516
Income taxes payable, short-term	20,064	20,008	20,044	19,892	19,142	18,198
Operating lease liabilities	4,724	4,576	4,463	5,194	6,357	7,382
Liabilities held for sale		0	0	0		14,620
Other current liabilities	18,559	22,306	17,924	16,715	18,893	15,854
Total current liabilities	85,864	90,882	83,458	80,063	86,179	88,293
Convertible notes, long-term	156,031	154,182	152,359	150,561	148,788	147,039
Long-term operating lease liabilities	34,305	35,973	37,626	38,074	39,889	9,415
Long-term income taxes payable	41,333	45,882	50,472	55,163	60,094	64,765
Deferred tax liabilities	14,276	15,090	14,675	14,140	13,846	13,724
Other long-term liabilities	6,894	8,714	12,818	15,792	19,272	15,308
Total liabilities	338,703	350,723	351,408	353,793	368,068	338,544
Commitments and contingencies (Notes 10, 13 and 20)
Stockholders’ equity:
Convertible preferred stock, $.001 par value: Authorized: 5,000,000 shares; Issued and outstanding: no shares at September 30, 2020, June 30, 2020, March 31, 2020 and September 30, 2019	0	0	0	0	0	0
Common Stock, $.001 par value: Authorized: 500,000,000 shares; Issued and outstanding: 113,922,520 shares at September 30, 2020, 113,743,652 shares at June 30, 2020, 113,275,229 shares at March 31, 2020 and 111,493,448 shares at September 30, 2019	112	114	114	113	112	111
Additional paid in capital	1,270,426	1,280,051	1,274,136	1,264,000	1,261,142	1,254,344
Accumulated deficit	(357,751)	(314,205)	(301,468)	(292,328)	(285,789)	(278,913)
Accumulated other comprehensive loss	(81)	(132)	(52)	(188)	(92)	(12,460)
Total stockholders’ equity	912,706	965,828	972,730	971,597	975,373	963,082	$ 973,226	$ 1,012,112	$ 571,584
Total liabilities and stockholders’ equity	$ 1,251,409	$ 1,316,551	$ 1,324,138	$ 1,325,390	$ 1,343,441	$ 1,301,626
Balance Sheet Parenthetical
Convertible preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001	$ 0.001	$ 0.001	$ 0.001	$ 0.001
Convertible preferred stock, authorized shares	5,000,000	5,000,000	5,000,000	5,000,000	5,000,000	5,000,000
Convertible preferred stock, issued shares	0	0	0	0	0	0
Convertible preferred stock, outstanding shares	0	0	0	0	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001	$ 0.001	$ 0.001	$ 0.001	$ 0.001
Common stock, authorized shares	500,000,000	500,000,000	500,000,000	500,000,000	500,000,000	500,000,000
Common stock, issued shares	111,697,994	113,922,520	113,743,652	113,275,229	112,131,352	111,493,448
Common stock, outstanding shares	111,697,994	113,922,520	113,743,652	113,275,229	112,131,352	111,493,448