Transitional Comparative Period (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended										6 Months Ended		12 Months Ended
	Jan. 27, 2018	Oct. 28, 2017	Jul. 29, 2017	Apr. 29, 2017	Jan. 28, 2017	Oct. 29, 2016	Jul. 30, 2016	Apr. 23, 2016	Jan. 23, 2016	Oct. 24, 2015	Jan. 27, 2018	Jan. 28, 2017	Jul. 29, 2017	Jul. 30, 2016	Jul. 25, 2015
Accounting Policies [Abstract]
Revenues	$ 655,133	$ 756,215	$ 780,188	$ 786,338	$ 701,131	$ 799,223	$ 789,159	$ 664,645	$ 559,470	$ 659,268	$ 1,411,348	$ 1,500,355	$ 3,066,880	$ 2,672,542	$ 2,022,312
EXPENSES:
Cost of earned revenue, excluding depreciation and amortization	540,633	600,847	606,898	621,475	561,371	614,990	605,909	520,408	450,284	506,978	1,141,480	1,176,361	2,404,734	2,083,579	1,593,250
General and administrative											124,930	118,395	239,231	217,149	178,700
Depreciation and amortization											85,053	70,252	147,906	124,940	96,044
Total											1,351,463	1,365,008	2,791,871	2,425,668	1,867,994
Interest expense, net											(19,560)	(18,248)	(37,364)	(34,720)	(27,025)
Other income, net											6,225	1,946	12,780	10,433	8,291
Income before income taxes											46,550	119,045	250,425	206,327	135,584
(Benefit) provision for income taxes											(22,285)	44,332	93,208	77,587	51,260
Net income	$ 40,059	$ 28,776	$ 43,708	$ 38,796	$ 23,663	$ 51,050	$ 49,360	$ 33,083	$ 15,473	$ 30,824	$ 68,835	$ 74,713	$ 157,217	$ 128,740	$ 84,324
Earnings per common share:
Basic earnings per common share (in dollars per share)	$ 1.29	$ 0.93	$ 1.41	$ 1.24	$ 0.75	$ 1.62	$ 1.57	$ 1.02	$ 0.47	$ 0.94	$ 2.22	$ 2.37	$ 5.01	$ 3.98	$ 2.48
Diluted earnings per common share (in dollars per share)	$ 1.24	$ 0.90	$ 1.38	$ 1.22	$ 0.74	$ 1.59	$ 1.54	$ 1.00	$ 0.46	$ 0.91	$ 2.15	$ 2.32	$ 4.92	$ 3.89	$ 2.41
Shares used in computing earnings per common share:
Basic (in shares)											31,059,140	31,480,660	31,351,367	32,315,636	34,045,481
Diluted (in shares)											32,054,945	32,180,923	31,984,731	33,115,755	35,026,688