Business Segment Information - Summary of financial information concerning reportable segments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from external customers	$ 830,437	$ 815,423	$ 1,652,879	$ 1,630,149
Net income attributable to CACI	30,338	24,642	64,140	55,772
Reportable Geographical Components | Domestic
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from external customers	793,542	779,352	1,579,220	1,558,883
Net income attributable to CACI	26,628	21,531	57,766	50,217
Reportable Geographical Components | International
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue from external customers	36,895	36,071	73,659	71,266
Net income attributable to CACI	$ 3,710	$ 3,111	$ 6,374	$ 5,555