Commitments and Contingencies (Insurance) (Details)	12 Months Ended
	Dec. 31, 2018 USD ($)
Insurance
Insurance maximum coverage per incident	$ 300,000,000
Insurance maximum coverage per property	300,000,000
All Risk Property And Rental Value
Insurance
Insurance maximum coverage per incident	1,700,000,000.0
Terrorism Coverage Including NBCR
Insurance
Insurance maximum coverage per incident	$ 1,700,000,000.0
Insurance coverage end date	Dec. 01, 2020
Insurance maximum coverage in aggregate	$ 1,700,000,000.0
NBCR
Insurance
Self Insured Responsibility (in percentage)	19.00%
Federal Government Responsibility (in percentage)	81.00%
FNSIC
Insurance
Insurance deductible	$ 323,000