Recently Issued Accounting Literature (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right-of-use assets	$ 457,662,000			$ 0
Lease liabilities	484,173,000			$ 0
Capitalized leasing costs		$ 1,348,000
Rental revenues	487,306,000
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right-of-use assets			$ 526,866,000
Lease liabilities			$ 526,866,000
Rental revenues	$ (890,000)