CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative effect adjustment of ASC 606	Common Stock	Additional Paid-in Capital	Retained Earnings	Retained Earnings Cumulative effect adjustment of ASC 606	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Total CACI Shareholders' Equity	Total CACI Shareholders' Equity Cumulative effect adjustment of ASC 606	Noncontrolling Interest
Beginning balance at Jun. 30, 2017	$ 1,793,721		$ 4,190	$ 569,080	$ 1,825,619		$ (29,116)	$ (576,187)	$ 1,793,586		$ 135
Beginning balance, shares at Jun. 30, 2017			41,896					17,435
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	301,171				301,171				301,171
Stock-based compensation expense	23,628			23,628					23,628
Tax withholdings on restricted share vestings	(21,344)		$ 24	(21,368)					(21,344)
Tax withholdings on restricted share vestings (in shares)			243
Change in fair value of interest rate swap agreements, net	7,473						7,473		7,473
Currency translation adjustment	1,986						1,986		1,986
Repurchases of common stock	(5,138)			(383)				$ (4,755)	(5,138)
Repurchases of common stock (in shares)								36
Treasury stock issued under stock purchase plans	4,763			7				$ 4,756	4,763
Treasury stock issued under stock purchase plans (in shares)								(37)
Post-retirement benefit costs	627						627		627
Ending balance at Jun. 30, 2018	2,106,887		$ 4,214	570,964	2,126,790		(19,030)	$ (576,186)	2,106,752		135
Ending balance, shares at Jun. 30, 2018			42,139					17,434
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	265,604				265,604				265,604
Stock-based compensation expense	25,272			25,272					25,272
Tax withholdings on restricted share vestings	(19,555)		$ 17	(19,572)					(19,555)
Tax withholdings on restricted share vestings (in shares)			175
Change in fair value of interest rate swap agreements, net	(17,914)						(17,914)		(17,914)
Currency translation adjustment	(6,103)						(6,103)		(6,103)
Repurchases of common stock	(5,838)			(392)				$ (5,446)	(5,838)
Repurchases of common stock (in shares)								34
Treasury stock issued under stock purchase plans	5,452			5				$ 5,447	5,452
Treasury stock issued under stock purchase plans (in shares)								(34)
Post-retirement benefit costs	(109)						(109)		(109)
Ending balance at Jun. 30, 2019	2,371,466	$ 17,770	$ 4,231	576,277	2,410,164	$ 17,770	(43,156)	$ (576,185)	2,371,331	$ 17,770	135
Ending balance, shares at Jun. 30, 2019			42,314					17,434
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	321,480				321,480				321,480
Stock-based compensation expense	29,302			29,302					29,302
Tax withholdings on restricted share vestings	(31,271)		$ 22	(31,293)					(31,271)
Tax withholdings on restricted share vestings (in shares)			211
Change in fair value of interest rate swap agreements, net	(24,280)						(24,280)		(24,280)
Currency translation adjustment	(4,990)						(4,990)		(4,990)
Repurchases of common stock	(7,806)			(622)				$ (7,184)	(7,806)
Repurchases of common stock (in shares)								34
Treasury stock issued under stock purchase plans	7,268			80				$ 7,188	7,268
Treasury stock issued under stock purchase plans (in shares)								(36)
Post-retirement benefit costs	141						141		141
Ending balance at Jun. 30, 2020	$ 2,661,310		$ 4,253	$ 573,744	$ 2,731,644		$ (72,285)	$ (576,181)	$ 2,661,175		$ 135
Ending balance, shares at Jun. 30, 2020			42,525					17,432