Subsequent Events - Revolving Credit Facility (Details) - Line of Credit - Revolving Credit Facility - Subsequent Event	Jul. 10, 2018 USD ($) covenant	Jul. 20, 2018 USD ($)
Subsequent Event [Line Items]
Maximum borrowing capacity	$ 100,000,000
Debt instrument, term	5 years
Accordion feature, increase limit	$ 125,000,000
Amount borrowed		$ 0
Commitment fee	0.20%
Number of financial covenants | covenant	2
Annual limit on capital expenditures	$ 100,000,000
Restrictive covenants, minimum voting ownership percentage	50.00%
Maximum repurchase of capital stock, amount	$ 75,000,000
Minimum capacity available	$ 20,000,000
Minimum
Subsequent Event [Line Items]
Restrictive covenants, minimum working capital ratio	2.00
Maximum
Subsequent Event [Line Items]
Restrictive covenants, minimum working capital ratio	1.00
Federal Funds Effective Swap Rate
Subsequent Event [Line Items]
Basis spread on variable rate	0.50%
Eurodollar
Subsequent Event [Line Items]
Basis spread on variable rate	1.00%
Applicable Margin, Base Rate Loans | Minimum
Subsequent Event [Line Items]
Basis spread on variable rate	0.00%
Applicable Margin, Base Rate Loans | Maximum
Subsequent Event [Line Items]
Basis spread on variable rate	0.75%
Applicable Margin, Eurodollar Rate Loans | Minimum
Subsequent Event [Line Items]
Basis spread on variable rate	1.00%
Applicable Margin, Eurodollar Rate Loans | Maximum
Subsequent Event [Line Items]
Basis spread on variable rate	1.75%