Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Jan. 30, 2021	Oct. 24, 2020	Jul. 25, 2020	Apr. 25, 2020	Jan. 25, 2020	Oct. 26, 2019	Jul. 27, 2019	Apr. 27, 2019	Jan. 30, 2021	Jan. 25, 2020	Jan. 26, 2019
Quarterly Financial Information Disclosure [Abstract]
Contract revenues	$ 750,665	$ 810,256	$ 823,921	$ 814,322	$ 737,603	$ 884,115	$ 884,221	$ 833,743	$ 3,199,165	$ 3,339,682	$ 3,127,700
Costs of earned revenues, excluding depreciation and amortization	645,476	658,355	657,953	680,206	633,203	724,378	720,382	701,767	2,641,989	2,779,730	2,562,392
Gross profit	105,189	151,901	165,968	134,116	104,400	159,737	163,839	131,976
Net Income	$ (4,195)	$ 33,926	$ 37,024	$ (32,418)	$ (11,189)	$ 24,229	$ 29,896	$ 14,279	$ 34,337	$ 57,215	$ 62,907
Basic earnings per common share (in dollars per share)	$ (0.13)	$ 1.06	$ 1.17	$ (1.03)	$ (0.35)	$ 0.77	$ 0.95	$ 0.45	$ 1.08	$ 1.82	$ 2.01
Diluted earnings per common share (in dollars per share)	$ (0.13)	$ 1.05	$ 1.15	$ (1.03)	$ (0.35)	$ 0.76	$ 0.94	$ 0.45	$ 1.07	$ 1.80	$ 1.97