Stock-Based Compensation - Summary of stock-based compensation expense recognized (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2014	Dec. 31, 2013
Stock-based compensation included in indirect costs and selling expenses:
Restricted stock and restricted stock unit (RSU) expense	$ 3,574us-gaap_RestrictedStockExpense	$ 3,301us-gaap_RestrictedStockExpense	$ 6,194us-gaap_RestrictedStockExpense	$ 5,744us-gaap_RestrictedStockExpense
Non-qualified stock option and stock settled stock appreciation right (SSAR) expense				41us-gaap_StockOptionPlanExpense
Total stock-based compensation expense	3,574	3,301	6,194	5,785
Income tax benefit recognized for stock-based compensation expense	$ 1,312	$ 1,278	$ 2,346	$ 2,225

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 1

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-Publisher SEC

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- Definition

The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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- Definition

The noncash expense that represents the cost of restricted stock or unit distributed to employees as compensation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

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- Definition

The noncash expense that accounts for the value of stock or unit options distributed to employees as compensation.

+ References

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