Fair Value Measurements (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Fair value measurements
Mortgage loans receivable	$ 165,444,000	$ 39,299,000
Senior unsecured notes	255,800,000	185,800,000
Contingent liabilities	0	6,744,000
Level 3 | Senior unsecured notes maturing prior to 2020
Fair value measurements
Discount rate (as a percent)	3.95%	3.80%
Level 3 | Senior unsecured notes maturing 2021
Fair value measurements
Discount rate (as a percent)	4.25%	4.30%
Level 3 | Contingent obligation under the earn-out liabilities
Fair value measurements
Discount rate (as a percent)		6.60%
Level 3 | Mortgage loans receivable
Fair value measurements
Discount rate (as a percent)	8.40%	6.00%
Carrying Value
Fair value measurements
Mortgage loans receivable	165,444,000	39,299,000
Bonds payable	2,035,000	2,635,000
Bank borrowings	21,000,000	115,500,000
Senior unsecured notes	255,800,000	185,800,000
Contingent liabilities		6,744,000
Fair Value
Fair value measurements
Bonds payable	2,035,000	2,635,000
Bank borrowings	21,000,000	115,500,000
Fair Value | Level 3
Fair value measurements
Mortgage loans receivable	200,248,000	44,939,000
Senior unsecured notes	262,351,000	194,838,000
Contingent liabilities		$ 6,744,000