Long-term Debt, Line of Credit and Derivatives - Financial covenants (Details)	3 Months Ended								6 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Dec. 31, 2017
Debt Instrument [Line Items]
Debt instrument, covenant, fixed charge coverage ratio, maximum		1.25
Debt instrument, covenant, leverage ratio, maximum		2.75	2.75	3.00	3.25	3.75	4.00	3.25
Scenario, Forecast
Debt Instrument [Line Items]
Debt instrument, covenant, leverage ratio, maximum	2.75								2.50