Fair Value Measurements (Fair Value Measurements on a Nonrecurring Basis) (Details) - USD ($)	Jun. 30, 2019	Dec. 31, 2018
Nonrecurring
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Right-of-use assets	$ 0
Level 1 | Nonrecurring
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Right-of-use assets	0
Level 2 | Nonrecurring
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Right-of-use assets	0
Level 3 | Nonrecurring
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Right-of-use assets	0
Real estate assets | Nonrecurring
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Real estate asset	67,102,000	$ 14,971,000
Real estate assets | Level 1 | Nonrecurring
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Real estate asset	0	0
Real estate assets | Level 2 | Nonrecurring
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Real estate asset	67,102,000	0
Real estate assets | Level 3 | Nonrecurring
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Real estate asset	0	$ 14,971,000
Valuation Technique, Discounted Cash Flow | 608 Fifth Avenue
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Real estate asset	$ 0