Other Assets (Details) $ in Thousands, £ in Millions	1 Months Ended						9 Months Ended	12 Months Ended
	Jun. 30, 2016 GBP (£)	Jun. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2012 GBP (£)	Jun. 30, 2012 USD ($)	Sep. 30, 2016 GBP (£)	Dec. 31, 2015 GBP (£)	Dec. 31, 2015 USD ($)	Sep. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 GBP (£)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 GBP (£)	Jun. 30, 2015 USD ($)
Other assets
Straight-line rent receivables, net of allowance										$ 380,178	$ 370,296
Allowance on straight-line rent receivables										30,776	33,648
Marketable debt securities, net										82,081	102,958
Leasing costs and inducements, net										155,889	158,708
Goodwill										50,346	50,346
Other										125,519	119,965
Total other assets										794,013	802,273
Loans receivables										682,994	768,743
Four Seasons Health Care
Other assets
Other-than-temporary impairment on securities			$ 70,000	$ 42,000
Debt Instrument, Face Amount | £					£ 175.0
Four Seasons
Other assets
Marketable debt securities, net							£ 49.0	£ 58.0		$ 64,000	$ 85,000	£ 66.0	$ 100,000	£ 111.0	$ 174,000
Marketable debt security, par value | £					138.5
Purchase of debt securities					£ 136.8	$ 215,000
Portion of debt held, as a percent.					79.00%	79.00%
Interest payment received	£ 8.0	$ 13,000						£ 8.0	$ 13,000
Annual interest rate (as a percent)							12.25%