Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Unamortized leasing fees to Vornado	$ 25,601	$ 27,851
Preferred stock: par value per share (in usd per share)	$ 1.00	$ 1.00
Preferred stock: authorized shares (in shares)	3,000,000	3,000,000
Preferred stock: issued shares (in shares)	0	0
Preferred stock: outstanding shares (in shares)	0	0
Common stock: par value per share (in usd per share)	$ 1.00	$ 1.00
Common stock: authorized shares (in shares)	10,000,000	10,000,000
Common stock: issued shares (in shares)	5,173,450	5,173,450
Common stock: outstanding shares (in shares)	5,107,290	5,107,290
Treasury stock: shares (in shares)	66,160	66,160