Long Term Debt (Convertible Notes Payable) (Narrative) (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified										12 Months Ended			12 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2009	Sep. 30, 2009	Jun. 30, 2009	Mar. 31, 2009	Dec. 31, 2008	Sep. 30, 2008	Jun. 30, 2011 Warrants [Member] Convertible Notes Payable [Member]	Jun. 30, 2011 Convertible Notes Payable [Member]	May 16, 2007 Convertible Notes Payable [Member]	Jun. 30, 2011 Convertible Notes Payable [Member] Call Options [Member]	Jun. 30, 2011 Convertible Notes Payable [Member] Non-Cash Interest Expense [Member]	Jun. 30, 2011 Warrants [Member]
Debt issuance date											May 16, 2007
Conversion rate of notes into shares											18.2989
Face value of convertible notes											$ 1,000
Initial conversion price per share	$ 54.65	$ 54.65	$ 54.65	$ 54.65	$ 54.65	$ 54.65	$ 54.65	$ 54.65	$ 54.65		$ 54.65
Debt conversion circumstances											1) if the last reported sale price of CACI stock is greater than or equal to 130 percent of the applicable conversion price for at least 20 trading days in the period of 30 consecutive trading days ending on the last trading day of the preceding fiscal quarter; 2) during the five consecutive business day period immediately after any ten consecutive trading day period (the note measurement period) in which the average of the trading price per $1,000 principal amount of convertible note was equal to or less than 97 percent of the average product of the closing price of a share of the Company's common stock and the conversion rate of each date during the note measurement period; 3) upon the occurrence of certain corporate events constituting a fundamental change, as defined in the indenture governing the Notes; or 4) during the last three-month period prior to maturity. CACI is required to satisfy 100 percent of the principal amount of these notes solely in cash, with any amounts above the principal amount to be satisfied in common stock
Convertible Notes effective interest rate											6.90%
Fair value of the liability component of notes												221,900,000
Proceed from notes payable											300,000,000
Fair value of equity components of notes											78,100,000
Debt discount amortization period											7
Unamortized debt discount	36,313,000	47,549,000
Fair value of the notes											379,500,000
Total debt issuance costs											7,800,000
Debt issuance cost amortized to interest expenses											5,800,000
Debt issuance costs attributable to conversion option											2,000,000
Debt issuance cost amortization period											7
Proceeds from sale of notes											45,500,000
Purchase of common stock											1.0		5.5
Purchase of call option													84,400,000
Income tax benefit on discount on issue of notes											32,800,000
Deferred tax liability														30,700,000
Common shares issuable under the sale of warrants											5.5
Warrants exercise price										$ 68.31					$ 68.31
Proceeds from sales of warrant										$ 56,500,000