CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 25, 2020	Jul. 27, 2019	Jul. 25, 2020	Jul. 27, 2019
Income Statement [Abstract]
Contract revenues	$ 823,921	$ 884,221	$ 1,638,244	$ 1,717,964
Costs of earned revenues, excluding depreciation and amortization	657,953	720,382	1,338,159	1,422,150
General and administrative	67,357	65,117	133,243	123,738
Depreciation and amortization	44,129	47,244	90,001	93,586
Goodwill impairment charge			53,264	0
Total	769,439	832,743	1,614,667	1,639,474
Interest expense, net	(7,853)	(12,878)	(20,310)	(25,111)
Gain (loss) on debt extinguishment	(458)	0	12,046	0
Other income, net	3,097	4,006	4,214	9,705
Income before income taxes	49,268	42,606	19,527	63,084
Provision for income taxes	12,244	12,710	14,921	18,909
Net income	$ 37,024	$ 29,896	$ 4,606	$ 44,175
Earnings per common share:
Basic earnings per common share (in dollars per share)	$ 1.17	$ 0.95	$ 0.15	$ 1.40
Diluted earnings per common share (in dollars per share)	$ 1.15	$ 0.94	$ 0.14	$ 1.39
Shares used in computing earnings per common share:
Basic (in shares)	31,750,547	31,487,011	31,677,012	31,469,401
Diluted (in shares)	32,128,098	31,820,296	31,947,346	31,803,368