Related Person Transactions - Footnotes to Revenue from Related Parties (Details) $ in Thousands	6 Months Ended
	Mar. 31, 2019 USD ($)
DHC
Related Party Transaction [Line Items]
Aggregate incentive business management fees	$ 40,642
SIR
Related Party Transaction [Line Items]
Aggregate incentive business management fees	25,817
SVC
Related Party Transaction [Line Items]
Aggregate incentive business management fees	$ 53,635