ACQUISITIONS (Estimated Fair Values of the Assets Acquired and Liabilities Assumed) (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021	Nov. 03, 2021	Jul. 23, 2021	Apr. 02, 2021
Business Acquisition [Line Items]
Goodwill	$ 521,267	$ 530,723
PolSource
Business Acquisition [Line Items]
Cash and cash equivalents					$ 2,565
Trade receivables and contract assets					12,734
Prepaid and other current assets					814
Goodwill					125,265
Intangible assets					15,790
Property and equipment and other noncurrent assets					461
Total assets acquired					157,629
Accounts payable, accrued expenses and other current liabilities					5,337
Short-term debt					0
Long-term debt					0
Operating lease liabilities, noncurrent					157
Other noncurrent liabilities					3,963
Total liabilities assumed					9,457
Noncontrolling interest in consolidated subsidiaries					0
Net assets acquired					$ 148,172
CORE
Business Acquisition [Line Items]
Cash and cash equivalents				$ 11,283
Trade receivables and contract assets				10,266
Prepaid and other current assets				5,490
Goodwill				23,237
Intangible assets				8,368
Property and equipment and other noncurrent assets				4,585
Total assets acquired				63,229
Accounts payable, accrued expenses and other current liabilities				8,439
Short-term debt				0
Long-term debt				0
Operating lease liabilities, noncurrent				2,056
Other noncurrent liabilities				2,525
Total liabilities assumed				13,020
Noncontrolling interest in consolidated subsidiaries				0
Net assets acquired				$ 50,209
Emakina
Business Acquisition [Line Items]
Cash and cash equivalents			$ 5,142
Trade receivables and contract assets			34,389
Prepaid and other current assets			3,109
Goodwill			137,037
Intangible assets			30,488
Property and equipment and other noncurrent assets			17,547
Total assets acquired			227,712
Accounts payable, accrued expenses and other current liabilities			36,411
Short-term debt			13,657
Long-term debt			8,874
Operating lease liabilities, noncurrent			5,527
Other noncurrent liabilities			8,756
Total liabilities assumed			73,225
Noncontrolling interest in consolidated subsidiaries			10,469
Net assets acquired			$ 144,018