Long-term Debt - Credit Facilities (Details) - USD ($)		4 Months Ended	12 Months Ended
	Jan. 28, 2020	Sep. 30, 2018	Dec. 31, 2019
Debt Instrument [Line Items]
Letters of credit outstanding			$ 32,700,000
Long-term Debt, Total			$ 384,823,000
Credit Facility [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Borrowing base limit	$ 250,000,000
Debt Instrument, Term	5 years
Limitation on billed accounts receivable, as a percent	87.50%
Limitation on unbilled accounts receivable, as a percent	85.00%
Limitation on net book value of equipment, as a percent	85.00%
Limitation on fair market value of real estate, as a percent	80.00%
Limitation alternative to real estate	$ 25,000,000
Fixed charge coverage ratio, as a percent	100.00%
Covenant testing trigger, as a percent	10.00%
Covenant testing trigger, amount	$ 20,000,000
Credit Facility [Member] | Minimum [Member]
Debt Instrument [Line Items]
Commitment fee, as a percent			0.25%
Credit Facility [Member] | Maximum [Member]
Debt Instrument [Line Items]
Commitment fee, as a percent			0.35%
Credit Facility [Member] | Base Rate Loans [Member] | Minimum [Member]
Debt Instrument [Line Items]
Quarterly adjustment to rate, as a percent			0.75%
Credit Facility [Member] | Base Rate Loans [Member] | Maximum [Member]
Debt Instrument [Line Items]
Quarterly adjustment to rate, as a percent			1.50%
Credit Facility [Member] | Base Rate Loans [Member] | Federal Funds Rate | Subsequent Event [Member]
Debt Instrument [Line Items]
Basis spread on variable rate, as a percent	0.50%
Credit Facility [Member] | Base Rate Loans [Member] | Prime Rate [Member]
Debt Instrument [Line Items]
Basis spread on variable rate, as a percent		1.25%
Credit Facility [Member] | Base Rate Loans [Member] | London Interbank Offered Rate (LIBOR) [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Basis spread on variable rate, as a percent	1.00%
Quarterly adjustment to rate, as a percent	0.50%
Credit Facility [Member] | Base Rate Loans [Member] | London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Quarterly adjustment to rate, as a percent	0.25%
Credit Facility [Member] | Base Rate Loans [Member] | London Interbank Offered Rate (LIBOR) [Member] | Maximum [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Quarterly adjustment to rate, as a percent	0.75%
Credit Facility [Member] | Eurodollar Rate Loans [Member] | Minimum [Member]
Debt Instrument [Line Items]
Quarterly adjustment to rate, as a percent			1.75%
Credit Facility [Member] | Eurodollar Rate Loans [Member] | Maximum [Member]
Debt Instrument [Line Items]
Quarterly adjustment to rate, as a percent			2.50%
Credit Facility [Member] | Eurodollar Rate Loans [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Basis spread on variable rate, as a percent		2.25%
Credit Facility [Member] | Eurodollar Rate Loans [Member] | London Interbank Offered Rate (LIBOR) [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Quarterly adjustment to rate, as a percent	1.50%
Credit Facility [Member] | Eurodollar Rate Loans [Member] | London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Quarterly adjustment to rate, as a percent	1.25%
Credit Facility [Member] | Eurodollar Rate Loans [Member] | London Interbank Offered Rate (LIBOR) [Member] | Maximum [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Quarterly adjustment to rate, as a percent	1.75%
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Borrowing capacity			$ 150,000,000
Letters of credit outstanding			32,700,000
Amount available to borrow			117,300,000
Amount outstanding			0
Revolving Credit Facility [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Borrowing capacity	$ 250,000,000
Commitment fee, as a percent	0.25%
Letter of Credit [Member]
Debt Instrument [Line Items]
Borrowing capacity			75,000,000
Letter of Credit [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Borrowing capacity	$ 75,000,000
Swingline Facility [Member]
Debt Instrument [Line Items]
Borrowing capacity			15,000,000
Swingline Facility [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Borrowing capacity	25,000,000
Term Facility [Member]
Debt Instrument [Line Items]
Borrowing capacity			200,000,000
Amount outstanding			$ 150,000,000
Term Facility [Member] | Minimum [Member]
Debt Instrument [Line Items]
Periodic payment, as a percentage of face amount			1.25%
Term Facility [Member] | Maximum [Member]
Debt Instrument [Line Items]
Periodic payment, as a percentage of face amount			2.50%
Accordion Facility [Member]
Debt Instrument [Line Items]
Borrowing capacity			$ 75,000,000
Accordion Facility [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Borrowing capacity	$ 75,000,000