Long-Term Debt and Credit Facility - Narrative (Details)		12 Months Ended
	Aug. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)	Mar. 12, 2018 USD ($)	Dec. 31, 2017 USD ($)	Oct. 31, 2015 USD ($)
Debt Instrument [Line Items]
Fees		$ 3,100,000
Up front lending fee		1,400,000
Third party arrangement fees		1,700,000
Other loans payable		1,000,000		$ 900,000
Repayments of lines of credit		7,000,000
Other long-term debt				7,800,000
Long-term debt fair value		$ 307,700,000		356,000,000
2015 Interest Rate Swap
Debt Instrument [Line Items]
Debt annualized rates (as percent)		3.79%
Notional amount					$ 262,500,000
Derivative fixed interest rate					1.46%
2018 Interest Rate Swap
Debt Instrument [Line Items]
Notional amount			$ 170,600,000.0
Amount of hedged item			$ 170,600,000
Derivative fixed interest rate			2.937%
2015 Credit Facility
Debt Instrument [Line Items]
Debt instrument face amount					$ 650,000,000
Credit facility borrowing capacity					350,000,000
Secure debt, outstanding		$ 282,200,000
Secure debt		308,400,000		308,400,000
Proceeds from (payments on) line of credit, net		31,000,000
Letters of credit outstanding		$ 27,900,000
Line of credit outstanding				$ 38,000,000
Amount of hedged item					$ 262,500,000
Credit facility maximum consolidated leverage ratio		3.5
Credit facility actual consolidated leverage ratio		2.94
Credit facility, remaining borrowing capacity		$ 61,600,000
Credit facility minimum consolidated fixed charge ratio		1.25
Credit facility actual consolidated fixed charge ratio		1.42
2015 Credit Facility | Insurance Carriers Collateral
Debt Instrument [Line Items]
Letters of credit outstanding		$ 12,300,000
2015 Credit Facility | Performance Guarantee
Debt Instrument [Line Items]
Letters of credit outstanding		$ 15,500,000
2015 Credit Facility | London Interbank Offered Rate (LIBOR) | Minimum
Debt Instrument [Line Items]
Debt basis spread on variable rate (as percent)		1.25%
2015 Credit Facility | London Interbank Offered Rate (LIBOR) | Maximum
Debt Instrument [Line Items]
Debt basis spread on variable rate (as percent)		2.25%
2015 Credit Facility | London Interbank Offered Rate (LIBOR) | 2015 Interest Rate Swap
Debt Instrument [Line Items]
Debt annualized rates (as percent)		4.45%
Term Loan
Debt Instrument [Line Items]
Credit facility borrowing capacity		$ 308,400,000.0
Term Loan | 2015 Credit Facility
Debt Instrument [Line Items]
Debt term		5 years
Line of Credit | 2015 Credit Facility
Debt Instrument [Line Items]
Credit facility borrowing capacity		$ 300,000,000.0
Line of credit facility expiration period		5 years
Maximum borrowing capacity, post sale		$ 275,000,000.0
Unamortized loan costs		2,400,000
Interest expense, debt		600,000
Proceeds from (payments on) line of credit, net		28,000,000
Bayou
Debt Instrument [Line Items]
Proceeds from divestiture of businesses	$ 46,000,000	35,000,000
Repayment from proceeds from divestiture of businesses		$ (35,000,000)