Long-Term Debt (Convertible Notes Payable) (Narrative) (Details) (USD $)	1 Months Ended	9 Months Ended	12 Months Ended					12 Months Ended		12 Months Ended		12 Months Ended
	Jun. 30, 2012	Mar. 31, 2012	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2010	Mar. 31, 2011	Jun. 30, 2012 Warrants [Member]	Jun. 30, 2012 Convertible Notes Payable [Member] Y	May 16, 2007 Convertible Notes Payable [Member]	Jun. 30, 2012 Convertible Notes Payable [Member] Call Options [Member]	Jun. 30, 2012 Convertible Notes Payable [Member] Non-Cash Interest Expense [Member]	Jun. 30, 2012 Convertible Notes Payable [Member] Warrants [Member]	Jun. 30, 2012 SSARs And Stock Options [Member] Y	Jun. 30, 2011 Restricted Stock And Restricted Stock Units [Member] Y	Jun. 30, 2012 Floating To Fixed Interest Rate Swap Agreements 1 [Member]	Jun. 30, 2012 Floating To Fixed Interest Rate Swap Agreements Two [Member]	Jun. 30, 2012 Cash Flow Hedging [Member]
Debt Instrument [Line Items]
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
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.
Effective interest rate for the Notes								6.90%
Fair value of the liability component of notes									221,900,000
Proceed from notes payable								300,000,000
Debt discount amortization period								7
Unamortized debt discount	24,289,000		24,289,000	36,313,000
Fair value of the notes	342,400,000		342,400,000
Total debt issuance costs								7,800,000
Debt issuance cost amortized to interest expense			19,219,000	18,430,000	17,694,000			5,800,000
Debt issuance costs attributable to conversion option								2,000,000
Debt issuance cost amortization period								7
Purchase of common stock										5,500,000
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								5,500,000
Warrants exercise price							$ 68.31					$ 68.31
Proceeds from sales of warrant												56,500,000
Number of floating to fixed interest rate swap agreements	2		2
Swap agreements															50,000,000	50,000,000	100,000,000
Common stock repurchased during the period, shares	2,000,000		6,000,000					1,000,000
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt								78,100,000
Proceeds from Loans								$ 45,500,000
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition													1.0	2.6