Short-Term Borrowings, Long-Term Debt, and Interest Expense - Interest Expense, Net (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Debt Disclosure [Abstract]
Interest expense	$ 3,967	$ 3,703	$ 11,592	$ 10,281
Deferred financing cost	107	107	322	322
Interest income	(30)	(18)	(93)	(50)
Less: amount capitalized for capital projects	(54)	(364)	(241)	(1,023)
Total interest expense, net	$ 3,990	$ 3,428	$ 11,580	$ 9,530