Leases (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Minimum Future Rental Receipts [Abstract]
2015	$ 341,950
2016	327,046
2017	300,418
2018	275,572
2019	248,604
Thereafter	6,203,163
Future Minimum Payments Receivable	7,696,753
Leaseholds Interests [Member]
Future Rental Payments [Abstract]
2015	5,137
2016	4,927
2017	4,880
2018	4,664
2019	4,134
Thereafter	37,963
Future Minimum Payments Due	61,705
Rent expense for leasehold interests	919	1,284	1,198
Corporate HQ and Office Space [Member]
Future Rental Payments [Abstract]
2015	1,261
2016	506
2017	1,256
2018	1,224
2019	1,224
Thereafter	8,019
Rent expense for leasehold interests	1,356	1,338	1,029
Incentive from lessor	$ 845