Long-Term Debt (Convertible Notes Payable) (Narrative) (Details) (USD $)	1 Months Ended		12 Months Ended					12 Months Ended		12 Months Ended		12 Months Ended			12 Months Ended
	Jul. 31, 2012	Jun. 30, 2012 agreement	Jun. 30, 2013	Jun. 30, 2012 agreement	Dec. 31, 2012	Dec. 31, 2011	Jun. 30, 2013 Warrants [Member]	Jun. 30, 2013 Convertible Notes Payable [Member]	May 16, 2007 Convertible Notes Payable [Member]	Jun. 30, 2013 Convertible Notes Payable [Member] Call Options [Member]	Jun. 30, 2013 Convertible Notes Payable [Member] Non-Cash Interest Expense [Member]	Jun. 30, 2013 Convertible Notes Payable [Member] Warrants [Member]	Jun. 30, 2012 Cash Flow Hedging [Member]	Jun. 30, 2012 Floating To Fixed Interest Rate Swap Agreements Two [Member]	Jun. 30, 2013 Minimum [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
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.
Threshold of share and conversion price			20 days
Measurement period for shares and conversion price			30 days
Percent of sale price of stock															130.00%
Note percent of average product closing price			97.00%
Threshold Of Note And Stock Price			5 days
Measurement Period For Shares And Notes Price			10 days
Percent of notes to be paid in cash			100.00%
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
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt								78,100,000
Debt discount amortization period								7 years
Unamortized debt discount		24,289,000	11,421,000	24,289,000
Fair value of the Notes			333,000,000
Value of Notes over principal if converted				48,400,000
Total debt issuance costs								7,800,000
Unamortized debt issuance expense		4,654,000	3,522,000	4,654,000	11,400,000	24,300,000		5,800,000
Debt issuance costs attributable to conversion option								2,000,000
Proceeds from Sale of Notes Receivable								45,500,000
Repurchases of common stock, shares	2,000,000	2,000,000						1,000,000
Purchase of call option										84,400,000
Purchase of common stock										5,500,000
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
Warrant's 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
Interest rate swap agreements													$ 100,000,000	$ 50,000,000