Long-term Debt, Line of Credit and Derivatives - Financial covenants (Details)	3 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Jun. 30, 2018
Debt Disclosure [Abstract]
Debt instrument, covenant, fixed charge coverage ratio, maximum								1.25
Debt instrument, covenant, leverage ratio, maximum	3.00	2.75	3.00	3.25	3.75	4.00	3.25