Business Segment Information - Summary of financial information concerning reportable segments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 977,274	$ 817,797	$ 2,630,153	$ 2,447,946
Net income attributable to CACI	34,028	29,039	98,168	84,811
Reportable Geographical Components
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	977,274	817,797	2,630,153	2,447,946
Net income attributable to CACI	34,028	29,039	98,168	84,811
Reportable Geographical Components | Domestic
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	940,714	781,618	2,519,934	2,340,501
Net income attributable to CACI	30,624	26,237	88,390	76,454
Reportable Geographical Components | International
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	36,560	36,179	110,219	107,445
Net income attributable to CACI	$ 3,404	$ 2,802	$ 9,778	$ 8,357