Dispositions (Assets and liabilities related to dispositions) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Dispositions
Assets related to discontinued operations (included in other assets)	$ 113	$ 1,357
Liabilities related to discontinued operations (included in other liabilities)	55	3,620
Income (loss) from discontinued operations:
Total revenues	1,114	261,290	$ 521,084
Total expenses	1,094	212,169	442,032
Income from discontinued operations before gain on sale of real estate	20	49,121	79,052
Net gains on sale of real estate, a lease position and other	618	6,605	20,376
JBGS spin-off transaction costs	0	(68,662)	(16,586)
Income (loss) from partially-owned entities	0	435	(3,559)
Net gain on early extinguishment of debt	0	0	487,877
Impairment losses	0	0	(161,165)
Pretax income (loss) from discontinued operations	638	(12,501)	405,995
Income tax expense	0	(727)	(1,083)
Income (loss) from discontinued operations	638	(13,228)	404,912
Cash flows related to discontinued operations:
Cash flows from operating activities	(1,683)	42,578	157,484
Cash flows from investing activities	$ 0	$ (48,377)	$ (216,125)