Debt - Aggregate Required Principal Payments (Details) - Mortgages - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Amortization
2019, amortization	$ 2,856
2020, amortization	3,938
2021, amortization	4,090
2022, amortization	5,628
2023, amortization	7,876
Thereafter, amortization	33,868
Total, amortization	58,256
Maturities
2019, maturities	250,000
2020, maturities	0
2021, maturities	0
2022, maturities	265,000
2023, maturities	0
Thereafter, maturities	1,355,422
Total, maturities	1,870,422
Total long term debt
2019	252,856
2020	3,938
2021	4,090
2022	270,628
2023	7,876
Thereafter	1,389,290
Total	$ 1,928,678	$ 1,929,612