Stock-Based Compensation - Summary of stock-based compensation expense recognized (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014
Stock-based compensation included in indirect costs and selling expenses:
Total stock-based compensation related to RSUs included in indirect costs and selling expense	$ 4,835	$ 3,574	$ 8,473	$ 6,194
Income tax benefit recognized for stock-based compensation expense	$ 1,734	$ 1,312	$ 3,177	$ 2,346