Goodwill (Details)	3 Months Ended	9 Months Ended
	Apr. 30, 2017 USD ($) operating_segment	Apr. 30, 2017 USD ($) operating_segment	Aug. 01, 2016 $ / shares
Goodwill [Line Items]
Balance as of July 31, 2016		$ 287,618,000
Changes resulting from TCS acquisition		3,015,000
Balance as of April 30, 2017	$ 290,633,000	$ 290,633,000
Number of reportable segments | operating_segment	2	2
Commercial Solutions Segment
Goodwill [Line Items]
Balance as of July 31, 2016		$ 229,273,000
Changes resulting from TCS acquisition		2,167,000
Balance as of April 30, 2017	$ 231,440,000	231,440,000
Reporting unit, percentage of fair value in excess of carrying amount			11.80%
Government Solutions Segment
Goodwill [Line Items]
Balance as of July 31, 2016		58,345,000
Changes resulting from TCS acquisition		848,000
Balance as of April 30, 2017	$ 59,193,000	$ 59,193,000
Reporting unit, percentage of fair value in excess of carrying amount			40.50%
Common Stock
Goodwill [Line Items]
Common stock price (in dollars per share) | $ / shares			$ 13.43