Other Assets (Details) $ in Thousands, £ in Millions	1 Months Ended					12 Months Ended
	Jun. 30, 2016 GBP (£)	Jun. 30, 2016 USD ($)	Dec. 31, 2015 GBP (£)	Dec. 31, 2015 USD ($)	Jun. 30, 2012 GBP (£)	Dec. 31, 2016 GBP (£)	Dec. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Jun. 30, 2012 USD ($)
Other assets
Straight-line rent receivables, net of allowance								$ 311,776	$ 366,951
Allowance on straight-line rent receivables								25,059	32,918
Loans receivable, net								807,954	768,743
Marketable debt securities, net								68,630	102,958
Leasing costs and inducements, net								156,820	158,708
Goodwill								42,386	47,019
Other								132,012	118,847
Total other assets								711,624	794,483
Four Seasons
Other assets
Loans receivable, net			£ 58.0			£ 42.0		$ 50,000	$ 85,000
Loan receivable, interest rate payable (as a percent)					12.25%					12.25%
Marketable debt security, par value | £					£ 138.5
Marketable debt security, par value, discounted					£ 136.8					$ 215,000
Marketable debt security, issued and outstanding as a percentage					79.00%
Marketable debt security, issued and outstanding | £					£ 175.0
Interest payment received	£ 8.0	$ 13,000	£ 8.0	$ 13,000		£ 8.0	$ 11,000