Condensed Consolidated Statements of Cash Flows - USD ($)	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
CASH FLOWS FROM (USED IN) OPERATING ACTIVITIES:
Net income	$ 68,937,000	$ 58,627,000
Adjustments to reconcile net income to net cash flow from (used in) operating activities:
Depreciation and amortization	37,887,000	33,154,000
Noncash lease expense	15,855,000	13,357,000
Stock-based compensation expense	7,556,000	5,510,000
Deferred income taxes	3,274,000	2,570,000
Change in allowance for bad debts	(999,000)	2,156,000
Contract loss reserve	0	(372,000)
Change in assets and liabilities—net of effects from acquired businesses:
Receivables—net	(56,912,000)	(46,198,000)
Prepaid expenses	(9,186,000)	(18,142,000)
Taxes receivable—current	5,247,000	15,410,000
Other current assets	401,000	1,026,000
Employee supplemental savings plan asset	(2,836,000)	(100,000)
Other long-term assets	(2,415,000)	(1,455,000)
Accounts payable	30,392,000	1,082,000
Operating lease obligations	(17,573,000)	(14,286,000)
Contract liabilities	(6,159,000)	20,146,000
Accrued expenses and other current liabilities	(5,896,000)	1,114,000
Accrued salaries and related expenses	1,330,000	17,613,000
Accrued retirement	(1,977,000)	(4,027,000)
Other long-term liabilities	(66,000)	17,687,000
Other	(312,000)	(195,000)
Net cash flow from operating activities	66,548,000	104,677,000
CASH FLOWS FROM (USED IN) INVESTING ACTIVITIES:
Purchases of property and equipment	(31,077,000)	(45,600,000)
Proceeds from corporate owned life insurance	227,000	4,137,000
Investment in capitalized software	0	(5,016,000)
Proceeds from sale of property and equipment	0	869,000
Net cash used in investing activities	(30,850,000)	(45,610,000)
CASH FLOWS FROM (USED IN) FINANCING ACTIVITIES:
Borrowing under revolving credit facility	164,000,000	261,500,000
Repayments under revolving credit facility	(149,000,000)	(278,000,000)
Dividends paid	(30,866,000)	(25,782,000)
Proceeds from exercise of stock options	6,433,000	4,882,000
Payment consideration to tax authority on employees' behalf	(2,493,000)	(777,000)
Principal paid on financing leases	(91,000)	(76,000)
Net cash flow used in financing activities	(12,017,000)	(38,253,000)
NET CHANGE IN CASH AND CASH EQUIVALENTS	23,681,000	20,814,000
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	41,193,000	8,854,000
CASH AND CASH EQUIVALENTS, END OF PERIOD	64,874,000	29,668,000
SUPPLEMENTAL CASH FLOW INFORMATION
Cash paid for interest	664,000	1,256,000
Cash paid for income taxes, net of refunds	12,864,000	(1,493,000)
Noncash investing and financing activities:
Operating lease obligations arising from obtaining right of use assets	9,496,000	303,000
Finance lease obligations arising from obtaining right of use assets	62,000	63,000
Noncash investing activities	$ (764,000)	$ 2,528,000