Notes Payable and Long-Term Debt, 2018 Credit Facility (Details) $ in Millions	Mar. 07, 2018 USD ($)
2018 Credit Facility [Member]
Notes Payable and Long-Term Debt [Abstract]
Secured credit facility	$ 250
Additional borrowing capacity under accordion feature	40
2018 First Lien Term Loan [Member]
Notes Payable and Long-Term Debt [Abstract]
Face amount	160
2018 Revolving Credit Facility [Member]
Notes Payable and Long-Term Debt [Abstract]
Maximum borrowing capacity	50
2018 Second Lien Term Loan [Member]
Notes Payable and Long-Term Debt [Abstract]
Face amount	$ 40