Real Estate Investments - Assets acquired and liabilities assumed (Details) (IOWA, USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014
Acquisitions and Dispositions [Line Items]
Building	$ 38.1
Total intangibles	1.6
Foreclosed mortgage note receivable	(40.0)
Other assets acquired	1.8
Accounts payable, accrued liabilities and other liabilities assumed	(1.7)
Cash acquired	0.2
Total cash paid	0
At-market lease intangibles
Acquisitions and Dispositions [Line Items]
Total intangibles	2.1
Finite-Lived Intangible Asset, Useful Life	5 years 9 months 18 days
Below Market Ground Lease Intangibles [Member]
Acquisitions and Dispositions [Line Items]
Total intangibles	(0.1)
Finite-Lived Intangible Asset, Useful Life	91 years 3 months 18 days
Below-market lease intangibles
Acquisitions and Dispositions [Line Items]
Total intangibles	$ (0.4)
Maximum | Below-market lease intangibles
Acquisitions and Dispositions [Line Items]
Finite-Lived Intangible Asset, Useful Life	6 years 6 months
Minimum | Below-market lease intangibles
Acquisitions and Dispositions [Line Items]
Finite-Lived Intangible Asset, Useful Life	3 years 9 months 18 days
Building [Member] | Maximum
Acquisitions and Dispositions [Line Items]
Property, Plant and Equipment, Useful Life	33 years
Building [Member] | Minimum
Acquisitions and Dispositions [Line Items]
Property, Plant and Equipment, Useful Life	11 years 6 months