Derivatives (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Stockholders' equity	$ (4,300,935)	$ (4,152,887)	$ (4,331,682)	$ (4,154,605)
Interest expense	33,670	29,957
Interest rate cash flow hedge gain (loss) to be reclassified over next 12 months, net	(2,555)
Reclassification out of other comprehensive income
Derivative [Line Items]
Interest expense	384	$ 323
AOCI, cash flow hedges
Derivative [Line Items]
Stockholders' equity	$ 18,362		$ 11,128