Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets
Cash and cash equivalents (Note 9)	$ 6,158	$ 4,831
Accounts receivable	143,827	119,504
Inventories	7,462	5,705
Prepaid income taxes	10,074	10,646
Prepaid expenses	23,150	19,154
Total current assets	190,671	159,840
Investments of deferred compensation plans held in trust (Note 14 and 16)	77,446	65,624
Properties and equipment, at cost, less accumulated depreciation (Note 12)	175,763	162,033
Lease right of use asset (Note 13)	111,652
Identifiable intangible assets less accumulated amortization of $37,620 (2018 - $33,283) (Note 6)	126,370	68,253
Goodwill	577,367	510,570
Other assets	9,048	9,209
Total Assets	1,268,317	975,529
Current liabilities
Accounts payable	51,101	50,150
Accrued insurance	50,328	46,095
Accrued compensation	70,814	63,329
Accrued legal	6,941	1,857
Short-term lease liability (Note 13)	39,280
Other current liabilities	43,756	30,239
Total current liabilities	262,220	191,670
Deferred income taxes (Note 11)	18,504	21,598
Long-term debt (Note 3)	90,000	89,200
Deferred compensation liabilities (Note 14)	76,446	64,616
Long-term lease liability (Note 13)	86,656
Other liabilities	7,883	17,111
Total Liabilities	541,709	384,195
Commitments and contingencies (Note 17)
Stockholders' Equity
Capital stock - authorized 80,000,000 shares $1 par; issued 35,810,528 shares (2018 - 35,311,418 shares)	35,811	35,311
Paid-in capital	860,671	774,358
Retained earnings	1,425,752	1,225,617
Treasury stock - 19,867,220 shares (2018 - 19,438,358 shares), at cost	(1,597,940)	(1,446,296)
Deferred compensation payable in Company stock (Note 14)	2,314	2,344
Total Stockholders' Equity	726,608	591,334
Total Liabilities and Stockholders' Equity	$ 1,268,317	$ 975,529