UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended				6 Months Ended		12 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Cash flows from operating activities:
Net income	$ 21,188	$ 13,261	$ 9,885	$ 9,106	$ 34,449	$ 18,991
Adjustments to reconcile net income to cash provided by operating activities:
Deferred income tax provision, net					899	(3,741)
Provision for credit losses					(181)	2,835
Depreciation and amortization					2,394	2,773
Stock-based compensation expense					6,936	5,799
Defined benefit pension plan expense					2,157	422
(Gain) loss on disposal or impairment of assets					(1,987)	1,092
Noncash lease expense					2,443	3,086
Loss on equity method investment					1,022	1,134
Other					445	600
Increase in operating assets
Trade receivables, net					(38,365)	(27,585)
Other assets					(4,890)	(2,510)
Increase in operating liabilities
Accrued payroll costs					17,002	10,588
Other liabilities					14,250	25,482
Cash provided by operating activities					36,574	38,966
Cash flows from investing activities:
Capital expenditures					(2,919)	(3,793)
Equity method investment					(4,500)	(2,500)
Proceeds from the sale of assets held within the Rabbi Trust					0	3,548
Net proceeds from the sale of assets					23,742	0
Cash provided by ( used in) investing activities					16,323	(2,745)
Cash flows from financing activities:
Proceeds from credit facility					0	35,000
Repurchases of common stock					(29,371)	(29,593)
Cash dividends					(9,532)	(8,455)
Payments on other financing arrangements					(201)	(633)
Cash used in financing activities					(39,104)	(3,681)
Change in cash and cash equivalents					13,793	32,540
Cash and cash equivalents, beginning of period		103,486		19,831	103,486	19,831	$ 19,831
Cash and cash equivalents, end of period	117,279		52,371		117,279	52,371	$ 103,486
Cash Paid During the Period For:
Income taxes					10,500	1,043
Operating lease liabilities					3,564	3,949
Interest, net					1,280	1,281
Non-Cash Investing and Financing Transactions:
ROU assets obtained from operating leases					3,852	2,971
Employee stock purchase plan	$ 195	$ 170	$ 134	$ 142	$ 365	$ 276