Mortgage Note Payable - Schedule of Long-term Debt Instruments (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Mortage notes payable	$ 281,186,000	$ 76,904,000
Unencumbered assets, carrying value	1,696,200,000
Mortgages
Debt Instrument [Line Items]
Encumbered properties	37
Mortage notes payable	281,186,000	76,904,000
Effective interest rate	3.70%
Rheinmetall | Mortgages
Debt Instrument [Line Items]
Encumbered properties	1
Mortage notes payable	12,884,000	0
Effective interest rate	2.50%
OBI DIY | Mortgages
Debt Instrument [Line Items]
Encumbered properties	1
Mortage notes payable	5,470,000	0
Effective interest rate	2.40%
RWE AG | Mortgages
Debt Instrument [Line Items]
Encumbered properties	3
Mortage notes payable	75,969,000	0
Effective interest rate	1.60%
Rexam | Mortgages
Debt Instrument [Line Items]
Encumbered properties	1
Mortage notes payable	6,394,000	0
Effective interest rate	1.90%
Metro Tonic | Mortgages
Debt Instrument [Line Items]
Encumbered properties	1
Mortage notes payable	32,211,000	0
Effective interest rate	1.70%
McDonald's | Mortgages
Debt Instrument [Line Items]
Encumbered properties	1
Mortage notes payable	1,180,000	1,253,000
Effective interest rate	4.10%
Wickes Building Supplies I | Mortgages
Debt Instrument [Line Items]
Encumbered properties	1
Mortage notes payable	3,024,000	3,209,000
Effective interest rate	3.70%
Everything Everywhere | Mortgages
Debt Instrument [Line Items]
Encumbered properties	1
Mortage notes payable	6,213,000	6,596,000
Effective interest rate	4.00%
Thames Water | Mortgages
Debt Instrument [Line Items]
Encumbered properties	1
Mortage notes payable	9,319,000	9,894,000
Effective interest rate	4.10%
Wickes Building Supplies II | Mortgages
Debt Instrument [Line Items]
Encumbered properties	1
Mortage notes payable	2,563,000	2,721,000
Effective interest rate	4.20%
Northern Rock | Mortgages
Debt Instrument [Line Items]
Encumbered properties	2
Mortage notes payable	8,155,000	8,657,000
Effective interest rate	4.40%
Wickes Building Supplies III | Mortgages
Debt Instrument [Line Items]
Encumbered properties	1
Mortage notes payable	2,951,000	3,133,000
Effective interest rate	4.30%
Provident Financial | Mortgages
Debt Instrument [Line Items]
Encumbered properties	1
Mortage notes payable	19,804,000	0
Effective interest rate	4.10%
Crown Crest | Mortgages
Debt Instrument [Line Items]
Encumbered properties	1
Mortage notes payable	29,901,000	0
Effective interest rate	4.20%
Aviva | Mortgages
Debt Instrument [Line Items]
Encumbered properties	1
Mortage notes payable	24,387,000	0
Effective interest rate	3.80%
Western Digital | Mortgages
Debt Instrument [Line Items]
Encumbered properties	1
Mortage notes payable	18,269,000	18,541,000
Effective interest rate	3.70%
Encanto Restaurants | Mortgages
Debt Instrument [Line Items]
Encumbered properties	18
Mortage notes payable	$ 22,492,000	$ 22,900,000
Effective interest rate	3.00%