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, 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	249,340			249,340			249,340
Stock-based compensation expense	18,183		18,183				18,183
Tax withholdings on restricted share vesting	(20,672)	$ 23	(20,695)				(20,672)
Tax withholdings on restricted share vesting (in shares)		231
Change in fair value of interest rate swap agreements, net	6,465				6,465		6,465
Currency translation adjustment	11,333				11,333		11,333
Repurchases of common stock	(3,802)		(303)			$ (3,499)	(3,802)
Repurchases of common stock (in shares)						27
Treasury stock issued under stock purchase plans	3,507		7			$ 3,500	3,507
Treasury stock issued under stock purchase plans (in shares)						(28)
Ending balance at Mar. 31, 2018	2,058,075	$ 4,213	566,272	2,074,959	(11,318)	$ (576,186)	2,057,940	135
Ending balance, shares at Mar. 31, 2018		42,127				17,434
Beginning balance at Dec. 31, 2017	1,986,820	$ 4,206	568,646	2,010,460	(20,441)	$ (576,186)	1,986,685	135
Beginning balance, shares at Dec. 31, 2017		42,059				17,434
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	64,499			64,499			64,499
Stock-based compensation expense	5,794		5,794				5,794
Tax withholdings on restricted share vesting	(8,036)	$ 7	(8,043)				(8,036)
Tax withholdings on restricted share vesting (in shares)		68
Change in fair value of interest rate swap agreements, net	3,344				3,344		3,344
Currency translation adjustment	5,779				5,779		5,779
Repurchases of common stock	(1,339)		(125)			$ (1,214)	(1,339)
Repurchases of common stock (in shares)						9
Treasury stock issued under stock purchase plans	1,214					$ 1,214	1,214
Treasury stock issued under stock purchase plans (in shares)						(9)
Ending balance at Mar. 31, 2018	2,058,075	$ 4,213	566,272	2,074,959	(11,318)	$ (576,186)	2,057,940	135
Ending balance, shares at Mar. 31, 2018		42,127				17,434
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 vesting	(18,796)	$ 16	(18,812)				(18,796)
Tax withholdings on restricted share vesting (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 vesting	(567)		(567)				(567)
Tax withholdings on restricted share vesting (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