Debt - Aggregate Required Principal Payments (Details) - Mortgages - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Amortization
2017, amortization	$ 1,983
2018, amortization	4,417
2019, amortization	3,790
2020, amortization	3,938
2021, amortization	4,090
Thereafter, amortization	43,407
Total, amortization	61,625
Maturities
2017, maturities	0
2018, maturities	262,210
2019, maturities	250,000
2020, maturities	0
2021, maturities	0
Thereafter, maturities	1,014,386
Total, maturities	1,526,596
Total long term debt
2017	1,983
2018	266,627
2019	253,790
2020	3,938
2021	4,090
Thereafter	1,057,793
Total	$ 1,588,221	$ 1,617,840