BUSINESS SEGMENT, CUSTOMER AND GEOGRAPHIC INFORMATION - Summarized Financial Information of Reportable Segments (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2014
Segment Reporting Information [Line Items]
Revenue from external customers	$ 1,137,389	$ 1,086,418	$ 1,057,530	$ 1,073,280	$ 1,113,900	$ 977,274	$ 830,437	$ 822,442	$ 4,354,617	$ 3,744,053	$ 3,313,452
Net income attributable to CACI	44,231	$ 40,357	$ 42,420	$ 36,663	43,599	$ 34,116	$ 30,452	$ 34,632	163,671	142,799	126,195
Net assets	1,793,721				1,607,313				1,793,721	1,607,313	1,480,272	$ 1,359,166
Goodwill	2,577,435				2,585,343				2,577,435	2,585,343	2,189,816
Total long-term assets	3,031,180				3,065,503				3,031,180	3,065,503	2,575,920
Total assets	3,911,082				3,987,341				3,911,082	3,987,341	3,242,030
Capital expenditures									43,268	20,835	17,444
Depreciation and amortization									71,760	64,752	66,083
Domestic Operations
Segment Reporting Information [Line Items]
Revenue from external customers									4,217,488	3,593,924	3,168,864
Net income attributable to CACI									150,271	129,568	114,658
Net assets	1,652,736				1,476,924				1,652,736	1,476,924	1,343,152
Goodwill	2,479,496				2,487,148				2,479,496	2,487,148	2,108,768
Total long-term assets	2,912,488				2,943,896				2,912,488	2,943,896	2,473,470
Total assets	3,716,893				3,798,013				3,716,893	3,798,013	3,055,782
Capital expenditures									41,832	18,339	15,324
Depreciation and amortization									67,042	60,637	61,587
International Operations
Segment Reporting Information [Line Items]
Revenue from external customers									137,129	150,129	144,588
Net income attributable to CACI									13,400	13,231	11,537
Net assets	140,985				130,389				140,985	130,389	137,120
Goodwill	97,939				98,195				97,939	98,195	81,048
Total long-term assets	118,692				121,607				118,692	121,607	102,450
Total assets	$ 194,189				$ 189,328				194,189	189,328	186,248
Capital expenditures									1,436	2,496	2,120
Depreciation and amortization									$ 4,718	$ 4,115	$ 4,496