Operating Information by Segment and Geographic Area - External Revenue and Segment Profit (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment reporting information
Revenue	$ 3,157,000	$ 3,103,000	$ 3,236,000	$ 2,939,000	$ 3,268,000	$ 3,457,000	$ 3,735,000	$ 3,698,000	$ 12,434,879	$ 14,157,929	$ 15,454,484
Segment profit (loss)									(59,730)	45,288	(828,335)
G&A									(216,451)	(201,522)	(139,819)
Impairment, restructuring & other exit costs									(43,792)	(108,357)	(318,442)
Gain (loss) on pension settlement									(198,000)	0	(138,000)
Foreign currency gain (loss)									(12,950)	(44,765)	(26,124)
Interest income (expense), net									(68,000)	(42,000)	(11,000)
Earnings (loss) from Cont Ops attributable to NCI									37,000	67,000	(39,000)
Earnings (loss) from Cont Ops before taxes	(157,000)	$ 70,000	$ (13,000)	$ (28,000)	(42,000)	$ 54,000	$ 23,000	$ (32,000)	(127,705)	3,494	(839,465)
Depreciation (all but Corporate included in segment profit)									73,200	102,451	154,599
Capital expenditures									75,073	113,442	180,842
Total assets	7,279,563				7,309,812				7,279,563	7,309,812
Goodwill	206,508				207,369				206,508	207,369
Cont Ops
Segment reporting information
Depreciation (all but Corporate included in segment profit)									68,000	81,000	75,000
Capital expenditures									50,000	61,000	74,000
Disc Ops - Assets held for sale	29,028				29,602				29,028	29,602
Disc Ops
Segment reporting information
Depreciation (all but Corporate included in segment profit)									5,417	21,849	78,771
Disc Ops - Assets held for sale	825,827				988,126				825,827	988,126
Reportable segments
Segment reporting information
Goodwill	207,000				207,000				207,000	207,000
Reportable segments | Cont Ops
Segment reporting information
Revenue									12,435,000	14,158,000	15,454,000
Segment profit (loss)									374,000	333,000	(167,000)
Intercompany revenue for our professional staffing business, excluded from revenue above | Cont Ops
Segment reporting information
Revenue									261,000	269,000	310,000
Energy Solutions | Reportable segments
Segment reporting information
Total assets	1,158,000				1,011,000				1,158,000	1,011,000
Goodwill	13,000				13,000				13,000	13,000
Energy Solutions | Reportable segments | Cont Ops
Segment reporting information
Revenue									4,956,000	5,271,000	5,838,000
Segment profit (loss)									250,000	169,000	(97,000)
Depreciation (all but Corporate included in segment profit)									0	0	0
Capital expenditures									0	0	0
Urban Solutions | Reportable segments
Segment reporting information
Total assets	906,000				1,123,000				906,000	1,123,000
Goodwill	130,000				130,000				130,000	130,000
Urban Solutions | Reportable segments | Cont Ops
Segment reporting information
Revenue									4,416,000	5,854,000	6,590,000
Segment profit (loss)									38,000	161,000	(50,000)
Depreciation (all but Corporate included in segment profit)									9,000	10,000	7,000
Capital expenditures									25,000	29,000	12,000
Mission Solutions | Reportable segments
Segment reporting information
Total assets	764,000				576,000				764,000	576,000
Goodwill	58,000				58,000				58,000	58,000
Mission Solutions | Reportable segments | Cont Ops
Segment reporting information
Revenue									3,063,000	3,033,000	3,026,000
Segment profit (loss)									155,000	87,000	46,000
Depreciation (all but Corporate included in segment profit)									4,000	4,000	4,000
Capital expenditures									4,000	3,000	3,000
Other | Reportable segments
Segment reporting information
Total assets	38,000				37,000				38,000	37,000
Goodwill	6,000				6,000				6,000	6,000
Other | Reportable segments | Cont Ops
Segment reporting information
Segment profit (loss)									(69,000)	(84,000)	(66,000)
Depreciation (all but Corporate included in segment profit)									2,000	2,000	2,000
Capital expenditures									2,000	4,000	1,000
Corporate | Reportable segments
Segment reporting information
Total assets	$ 3,588,000				$ 3,575,000				3,588,000	3,575,000
Corporate | Reportable segments | Cont Ops
Segment reporting information
Depreciation (all but Corporate included in segment profit)									53,000	65,000	62,000
Capital expenditures									19,000	25,000	58,000
Diversified Services Segment | Reportable segments | Cont Ops
Segment reporting information
Depreciation (all but Corporate included in segment profit)									5,000	22,000	79,000
Capital expenditures									$ 28,000	$ 48,000	$ 102,000