CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (UNAUDITED) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Total CACI Shareholders' Equity	Noncontrolling Interest
Beginning balance at Jun. 30, 2019	$ 2,371,466	$ 4,231	$ 576,277	$ 2,410,164	$ (43,156)	$ (576,185)	$ 2,371,331	$ 135
Beginning balance, shares at Jun. 30, 2019		42,314				17,434
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	227,749			227,749			227,749
Stock-based compensation expense	22,204		22,204				22,204
Tax withholdings on restricted share vestings	(30,439)	$ 21	(30,460)				(30,439)
Tax withholdings on restricted share vestings (in shares)		204
Change in fair value of interest rate swap agreements, net	(22,402)				(22,402)		(22,402)
Currency translation adjustment	(4,663)				(4,663)		(4,663)
Repurchases of common stock	(5,584)		(369)			$ (5,215)	(5,584)
Repurchases of common stock (in shares)						24
Treasury stock issued under stock purchase plans	5,299		80			$ 5,219	5,299
Treasury stock issued under stock purchase plans (in shares)						(26)
Ending balance at Mar. 31, 2020	2,563,630	$ 4,252	567,732	2,637,913	(70,221)	$ (576,181)	2,563,495	135
Ending balance, shares at Mar. 31, 2020		42,518				17,432
Beginning balance at Dec. 31, 2019	2,508,580	$ 4,250	561,521	2,557,336	(38,478)	$ (576,184)	2,508,445	135
Beginning balance, shares at Dec. 31, 2019		42,505				17,434
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	80,577			80,577			80,577
Stock-based compensation expense	7,705		7,705				7,705
Tax withholdings on restricted share vestings	(1,369)	$ 2	(1,371)				(1,369)
Tax withholdings on restricted share vestings (in shares)		13
Change in fair value of interest rate swap agreements, net	(21,173)				(21,173)		(21,173)
Currency translation adjustment	(10,570)				(10,570)		(10,570)
Repurchases of common stock	(1,988)		(190)			$ (1,798)	(1,988)
Repurchases of common stock (in shares)						7
Treasury stock issued under stock purchase plans	1,868		67			$ 1,801	1,868
Treasury stock issued under stock purchase plans (in shares)						(9)
Ending balance at Mar. 31, 2020	2,563,630	$ 4,252	567,732	2,637,913	(70,221)	$ (576,181)	2,563,495	135
Ending balance, shares at Mar. 31, 2020		42,518				17,432
Beginning balance at Jun. 30, 2020	2,661,310	$ 4,253	573,744	2,731,644	(72,285)	$ (576,181)	2,661,175	135
Beginning balance, shares at Jun. 30, 2020		42,525				17,432
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	320,466			320,466			320,466
Stock-based compensation expense	23,841		23,841				23,841
Tax withholdings on restricted share vestings	(19,486)	$ 14	(19,500)				(19,486)
Tax withholdings on restricted share vestings (in shares)		147
Change in fair value of interest rate swap agreements, net	11,363				11,363		11,363
Currency translation adjustment	21,946				21,946		21,946
Repurchases of common stock	(506,629)		(100,065)			$ (406,564)	(506,629)
Repurchases of common stock (in shares)						1,721
Treasury stock issued under stock purchase plans	6,583		19			$ 6,564	6,583
Treasury stock issued under stock purchase plans (in shares)						(31)
Ending balance at Mar. 31, 2021	2,519,394	$ 4,267	478,039	3,052,110	(38,976)	$ (976,181)	2,519,259	135
Ending balance, shares at Mar. 31, 2021		42,672				19,122
Beginning balance at Dec. 31, 2020	2,884,279	$ 4,266	570,176	2,931,766	(45,883)	$ (576,181)	2,884,144	135
Beginning balance, shares at Dec. 31, 2020		42,663				17,432
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	120,344			120,344			120,344
Stock-based compensation expense	8,800		8,800				8,800
Tax withholdings on restricted share vestings	(904)	$ 1	(905)				(904)
Tax withholdings on restricted share vestings (in shares)		9
Change in fair value of interest rate swap agreements, net	6,467				6,467		6,467
Currency translation adjustment	440				440		440
Repurchases of common stock	(502,209)		(100,032)			$ (402,177)	(502,209)
Repurchases of common stock (in shares)						1,699
Treasury stock issued under stock purchase plans	2,177					$ 2,177	2,177
Treasury stock issued under stock purchase plans (in shares)						(9)
Ending balance at Mar. 31, 2021	$ 2,519,394	$ 4,267	$ 478,039	$ 3,052,110	$ (38,976)	$ (976,181)	$ 2,519,259	$ 135
Ending balance, shares at Mar. 31, 2021		42,672				19,122