Real Estate (Dispositions) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) property	Dec. 31, 2015 USD ($) property		Dec. 31, 2014 USD ($) property
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax expense	$ 0	$ (10,318)		$ 75
Discontinued operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on disposition of real estate	0	0		155	[1]
Income tax expense	$ 0	$ 0		$ 0
Number of sold properties | property	0	0		2
Gain on disposition of assets, total, continuing and discontinued operations	$ 27,182	$ 10,450		$ 11,424
Assets Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Sold Properties | property	38	19		25
Gain on disposition of real estate	$ 27,182	$ 10,807	[1]	$ 11,587
Income tax expense	0	(357)		(318)
Gain on disposition of real estate, net of income tax expense	$ 27,182	$ 10,450		$ 11,269
Assets Held-for-sale | Discontinued operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of sold properties | property	5

[1] Amount includes the recognition of deferred gains on previously sold properties.