Long-Term Debt and Financing Obligations Long-term Debt Maturities (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Year One	$ 100,600	[1]
Long-term Debt, Maturities, Repayments of Principal in Year Two	45,000
Long-term Debt, Maturities, Repayments of Principal in Year Three	0
Long-term Debt, Maturities, Repayments of Principal in Year Four	150,000
Long-term Debt, Maturities, Repayments of Principal in Year Five	$ 0

[1] The 7.25% 2009 Series A and the 7.25% 2009 Series B PCBs with an aggregate principal amount, together, of $100.6 million have optional redemptions beginning in February 2019 and April 2019, respectively, at which time the Company expects to repay, remarket or replace these bonds.