Subsequent Events (Details) - USD ($) $ / shares in Units, $ in Thousands					12 Months Ended
	Feb. 13, 2019	Jan. 31, 2019	Nov. 12, 2015	Oct. 30, 2015	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 10, 2019
Subsequent events
Dividends declared for common stock (in dollars per share)			$ 2.00	$ 2.00	$ 2.97	$ 2.87	$ 2.75
Fashion Outlets of Chicago
Subsequent events
Interest rate (as a percent)					4.01%
Subsequent event
Subsequent events
Dividends declared for common stock (in dollars per share)		$ 0.75
Subsequent event | Fashion Outlets of Chicago
Subsequent events
Mortgage loan								$ 300,000
Interest rate (as a percent)								4.58%
SanTan Village Regional Center | Subsequent event
Subsequent events
Mortgage loan	$ 220,000
Interest rate on debt (as a percent)	4.30%
Interest rate on debt, term	10 years