Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 27, 2019	Sep. 28, 2018
Cash flows from operating activities:
Net income	$ 63,339	$ 56,218
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of property, equipment and leasehold improvements	4,904	4,710
Amortization of premiums and accretion of discounts on short-term investments	(442)	(51)
Deferred rent		(87)
Provision for contract losses and doubtful accounts	2,146	1,359
Stock-based compensation	13,585	13,605
Deferred income tax provision	(1,671)	(2,510)
Changes in operating assets and liabilities:
Accounts receivable	(24,665)	(14,170)
Prepaid expenses and other current assets	(5,604)	(8,999)
Change in operating leases	24
Accounts payable and accrued liabilities	3,102	(3,609)
Accrued payroll and employee benefits	(2,159)	(202)
Deferred revenues	(266)	562
Net cash provided by operating activities	52,293	46,826
Cash flows from investing activities:
Capital expenditures	(17,024)	(12,170)
Purchase of short-term investments	(38,693)	(37,788)
Maturity of short-term investments	44,000	28,000
Net cash used in investing activities	(11,717)	(21,958)
Cash flows from financing activities:
Payroll taxes for restricted stock units	(11,183)	(8,839)
Exercise of stock-based payment awards	1,969	1,065
Dividends and dividend equivalents rights	(25,223)	(20,497)
Net cash used in financing activities	(34,437)	(28,271)
Effect of foreign currency exchange rates on cash and cash equivalents	(355)	(414)
Net increase (decrease) in cash and cash equivalents	5,784	(3,817)
Cash and cash equivalents at beginning of period	127,059	124,794
Cash and cash equivalents at end of period	$ 132,843	$ 120,977