CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended										6 Months Ended		12 Months Ended
	Jan. 26, 2019	Oct. 27, 2018	Jul. 28, 2018	Apr. 28, 2018	Jan. 27, 2018	Oct. 28, 2017	Jul. 29, 2017	Apr. 29, 2017	Jan. 28, 2017	Oct. 29, 2016	Jan. 27, 2018	Jan. 28, 2017	Jan. 26, 2019	Jul. 29, 2017	Jul. 30, 2016
REVENUES:
Contract revenues	$ 748,619	$ 848,237	$ 799,470	$ 731,375	$ 655,133	$ 756,215	$ 780,188	$ 786,338	$ 701,131	$ 799,223	$ 1,411,348	$ 1,500,355	$ 3,127,700	$ 3,066,880	$ 2,672,542
EXPENSES:
Costs of earned revenues, excluding depreciation and amortization	633,279	687,164	642,376	599,573	540,633	600,847	606,898	621,475	561,371	614,990	1,141,480	1,176,361	2,562,392	2,404,734	2,083,579
General and administrative (including stock-based compensation expense of $20.2 million, $13.3 million, $20.8 million, and $16.8 million, respectively)											124,930	118,395	269,140	239,231	217,149
Depreciation and amortization											85,053	70,252	179,603	147,906	124,940
Total											1,351,463	1,365,008	3,011,135	2,791,871	2,425,668
Interest expense, net											(19,560)	(18,248)	(44,369)	(37,364)	(34,720)
Loss on debt extinguishment											0		0	0	(16,260)
Other income, net											6,225	1,946	15,842	12,780	10,433
Income before income taxes											46,550	119,045	88,038	250,425	206,327
Provision (benefit) for income taxes:
Current											(2,620)		16,608	74,975	50,805
Deferred											(19,665)		8,523	18,233	26,782
Total provision for income taxes											(22,285)	44,332	25,131	93,208	77,587
Net income	$ (12,054)	$ 27,830	$ 29,900	$ 17,231	$ 40,059	$ 28,776	$ 43,708	$ 38,796	$ 23,663	$ 51,050	$ 68,835	$ 74,713	$ 62,907	$ 157,217	$ 128,740
Earnings per common share:
Basic earnings per common share (in dollars per share)	$ (0.38)	$ 0.89	$ 0.96	$ 0.55	$ 1.29	$ 0.93	$ 1.41	$ 1.24	$ 0.75	$ 1.62	$ 2.22	$ 2.37	$ 2.01	$ 5.01	$ 3.98
Diluted earnings per common share (in dollars per share)	$ (0.38)	$ 0.87	$ 0.94	$ 0.53	$ 1.24	$ 0.90	$ 1.38	$ 1.22	$ 0.74	$ 1.59	$ 2.15	$ 2.32	$ 1.97	$ 4.92	$ 3.89
Shares used in computing earnings per common share:
Basic (in shares)											31,059,140	31,480,660	31,250,376	31,351,367	32,315,636
Diluted (in shares)											32,054,945	32,180,923	31,990,168	31,984,731	33,115,755