Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Leases, Future Minimum Payments Receivable [Abstract]
Operating Leases, Future Minimum Payments Receivable, Current	$ 332,593
Operating Leases, Future Minimum Payments Receivable, in Two Years	318,103
Operating Leases, Future Minimum Payments Receivable, in Three Years	292,463
Operating Leases, Future Minimum Payments Receivable, in Four Years	254,603
Operating Leases, Future Minimum Payments Receivable, in Five Years	215,625
Operating Leases, Future Minimum Payments Receivable, Thereafter	$ 664,727
Number of centers with option to extend lease term for three 10-year periods	one
Number of centers with option to extend lease term for one 10-year period	one
Lessee, Operating Lease, Renewal Term	10 years
Operating Leases, Rent Expense	$ 20,100	$ 15,100	$ 15,400
Operating Leases, Rent Expense, Contingent Rentals	0	0	$ 0
Payables representing straightline rent adjustments under lease agreements	62,600	$ 59,300
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Operating Leases, Future Minimum Payments Due, Next Twelve Months	15,484
Operating Leases, Future Minimum Payments, Due in Two Years	15,427
Operating Leases, Future Minimum Payments, Due in Three Years	14,288
Operating Leases, Future Minimum Payments, Due in Four Years	12,740
Operating Leases, Future Minimum Payments, Due in Five Years	13,982
Operating Leases, Future Minimum Payments, Due Thereafter	$ 737,210
City Creek Center [Member]
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Company's ownership in leasehold interest	100.00%