CONSOLIDATED STATEMENTS OF CASH FLOWS $ in Thousands	6 Months Ended
	Jul. 27, 2019 USD ($)	Jul. 28, 2018 USD ($)
Statement of Cash Flows [Abstract]
Interest Paid, Excluding Capitalized Interest, Operating Activities	$ 13,318	$ 9,292
Cash flows from operating activities:
Net income	44,175	47,131
Adjustments to reconcile net income to net cash provided by operating activities, net of acquisitions:
Depreciation and amortization	93,586	88,160
Non-cash lease expense	14,804	0
Deferred income tax provision	11,605	7,055
Stock-based compensation	5,756	10,911
Provision for bad debt (recovery), net	(10,514)	(38)
Gain on sale of fixed assets	(11,544)	(13,324)
Amortization of debt discount	9,947	9,422
Amortization of debt issuance costs and other	1,986	1,789
Change in operating assets and liabilities:
Accounts receivable, net	(171,486)	(48,835)
Contract assets, net	(143,558)	(110,478)
Other current assets and inventories	(15,378)	(12,842)
Other assets	37,036	718
Income taxes receivable/payable	3,876	6,964
Accounts payable	21,645	24,276
Accrued liabilities, insurance claims, operating lease liabilities, and other liabilities	(1,674)	26,280
Net cash provided by operating activities	(109,738)	37,189
Cash flows from investing activities:
Cash paid for acquisitions, net of cash acquired	0	(20,917)
Capital expenditures	(83,944)	(80,537)
Proceeds from sale of assets	12,780	14,965
Other investing activities	306	1,576
Net cash used in investing activities	(70,858)	(84,913)
Proceeds from Long-term Lines of Credit	146,000	60,000
Cash flows from financing activities:
Principal payments on senior credit agreement, including term loans	(81,000)	(72,031)
Exercise of stock options	182	381
Restricted stock tax withholdings	(845)	(93)
Net cash provided by (used in) financing activities	64,337	(11,743)
Net decrease in cash and equivalents and restricted cash	(116,259)	(59,467)
Cash and equivalents and restricted cash at beginning of period	134,151	90,182
Cash and equivalents and restricted cash at end of period	17,892	30,715
SUPPLEMENTAL DISCLOSURE OF OTHER CASH FLOW ACTIVITIES AND NON-CASH INVESTING AND FINANCING ACTIVITIES:
Cash paid for taxes, net	4,361	4,594
Purchases of capital assets included in accounts payable or other accrued liabilities at period end	$ 5,288	8,934
0.75% Convertible Senior Notes Due 2021 [Member]
Debt Instrument, Interest Rate, Stated Percentage	0.75%
Adjustments to reconcile net income to net cash provided by operating activities, net of acquisitions:
Amortization of debt discount	$ 9,900	$ 9,400