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, 2018	$ 2,106,887	$ 4,214	$ 570,964	$ 2,126,790	$ (19,030)	$ (576,186)	$ 2,106,752	$ 135
Beginning balance, shares at Jun. 30, 2018		42,139				17,434
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	215,574			215,574			215,574
Stock-based compensation expense	18,351		18,351				18,351
Tax withholdings on restricted share vestings	(18,796)	$ 16	(18,812)				(18,796)
Tax withholdings on restricted share vestings (in shares)		165
Change in fair value of interest rate swap agreements, net	(5,636)				(5,636)		(5,636)
Currency translation adjustment	(2,372)				(2,372)		(2,372)
Repurchases of common stock	(4,310)		(301)			$ (4,009)	(4,310)
Repurchases of common stock (in shares)						26
Treasury stock issued under stock purchase plans	4,015		5			$ 4,010	4,015
Treasury stock issued under stock purchase plans (in shares)						(26)
Ending balance at Mar. 31, 2019	2,331,483	$ 4,230	570,207	2,360,134	(27,038)	$ (576,185)	2,331,348	135
Ending balance, shares at Mar. 31, 2019		42,304				17,434
Beginning balance at Dec. 31, 2018	2,256,733	$ 4,230	564,586	2,291,989	(28,022)	$ (576,185)	2,256,598	135
Beginning balance, shares at Dec. 31, 2018		42,296				17,434
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	68,145			68,145			68,145
Stock-based compensation expense	6,304		6,304				6,304
Tax withholdings on restricted share vestings	(567)		(567)				(567)
Tax withholdings on restricted share vestings (in shares)		8
Change in fair value of interest rate swap agreements, net	(2,075)				(2,075)		(2,075)
Currency translation adjustment	3,059				3,059		3,059
Repurchases of common stock	(1,554)		(116)			$ (1,438)	(1,554)
Repurchases of common stock (in shares)						11
Treasury stock issued under stock purchase plans	1,438					$ 1,438	1,438
Treasury stock issued under stock purchase plans (in shares)						(11)
Ending balance at Mar. 31, 2019	2,331,483	$ 4,230	570,207	2,360,134	(27,038)	$ (576,185)	2,331,348	135
Ending balance, shares at Mar. 31, 2019		42,304				17,434
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect adjustment of ASC 606, net of taxes	17,770			17,770			17,770
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