Real Estate Investments - Assets acquired and liabilities assumed (Details) (IOWA, USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	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 [Member]
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 [Member] | Below-market lease intangibles
Acquisitions and Dispositions [Line Items]
Finite-Lived Intangible Asset, Useful Life	6 years 6 months
Minimum [Member] | Below-market lease intangibles
Acquisitions and Dispositions [Line Items]
Finite-Lived Intangible Asset, Useful Life	3 years 9 months 18 days
Building [Member] | Maximum [Member]
Acquisitions and Dispositions [Line Items]
Property, Plant and Equipment, Useful Life	33 years
Building [Member] | Minimum [Member]
Acquisitions and Dispositions [Line Items]
Property, Plant and Equipment, Useful Life	11 years 6 months