Subsequent Events (Narrative) (Details) $ / shares in Units, $ in Thousands		3 Months Ended
	Feb. 22, 2019 USD ($) ft² $ / shares	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018 USD ($)
Subsequent Event [Line Items]
Dividends payable, date payable		Oct. 05, 2017	Jul. 06, 2017	Apr. 05, 2017	Jan. 05, 2017
Dividends payable, date of record		Sep. 22, 2017	Jun. 16, 2017	Mar. 16, 2017	Dec. 16, 2016
Assets held for sale | $						$ 71,800
Liabilities held for sale | $						$ 24,349
Subsequent Event
Subsequent Event [Line Items]
Acres Of Land Contributed | ft²	118,000
Dividends payable, date declared	Feb. 22, 2019
Dividends payable, date payable	Apr. 04, 2019
Dividends payable, date of record	Mar. 20, 2019
Cash dividend payable per common share | $ / shares	$ 0.44
Assets held for sale | $	$ 71,800
Subsequent Event | Series B Preferred Stock
Subsequent Event [Line Items]
Dividends payable, date declared	Feb. 22, 2019
Dividends payable, date payable	Apr. 15, 2019
Dividends payable, date of record	Mar. 31, 2019
Cash dividend payable per common share | $ / shares	$ 1.63
Subsequent Event | Series A Preferred Stock
Subsequent Event [Line Items]
Dividends payable, date declared	Feb. 22, 2019
Dividends payable, date payable	Apr. 15, 2019
Dividends payable, date of record	Mar. 31, 2019
Cash dividend payable per common share | $ / shares	$ 0.45