Long-Term Debt Long-Term Debt (Details 3) $ in Thousands	Dec. 31, 2018 USD ($)
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate at Period End	2.75%
Letters of credit outstanding	$ 24,335
Bilateral Letter of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate at Period End	1.75%
Letters of credit outstanding	$ 19,053