4. Debt Applicable Margin of Unsecured Term Loan (Details) - Unsecured Term Loan [Member]	3 Months Ended
	Mar. 31, 2017
London Interbank Offered Rate (LIBOR) [Member] | Pricing Level 1 [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.50%
London Interbank Offered Rate (LIBOR) [Member] | Pricing Level 2 [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.60%
London Interbank Offered Rate (LIBOR) [Member] | Pricing Level 3 [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.75%
London Interbank Offered Rate (LIBOR) [Member] | Pricing Level 4 [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.90%
London Interbank Offered Rate (LIBOR) [Member] | Pricing Level 5 [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.10%
Base Rate [Member] | Pricing Level 1 [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.50%
Base Rate [Member] | Pricing Level 2 [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.60%
Base Rate [Member] | Pricing Level 3 [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.75%
Base Rate [Member] | Pricing Level 4 [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.90%
Base Rate [Member] | Pricing Level 5 [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.10%
Maximum [Member]
Debt Instrument [Line Items]
Ratio of Total Indebtedness To Gross Assets Value	60.00%
Maximum [Member] | Pricing Level 1 [Member]
Debt Instrument [Line Items]
Ratio of Total Indebtedness To Gross Assets Value	35.00%
Maximum [Member] | Pricing Level 2 [Member]
Debt Instrument [Line Items]
Ratio of Total Indebtedness To Gross Assets Value	40.00%
Maximum [Member] | Pricing Level 3 [Member]
Debt Instrument [Line Items]
Ratio of Total Indebtedness To Gross Assets Value	45.00%
Maximum [Member] | Pricing Level 4 [Member]
Debt Instrument [Line Items]
Ratio of Total Indebtedness To Gross Assets Value	52.50%
Minimum [Member] | Pricing Level 2 [Member]
Debt Instrument [Line Items]
Ratio of Total Indebtedness To Gross Assets Value	35.00%
Minimum [Member] | Pricing Level 3 [Member]
Debt Instrument [Line Items]
Ratio of Total Indebtedness To Gross Assets Value	40.00%
Minimum [Member] | Pricing Level 4 [Member]
Debt Instrument [Line Items]
Ratio of Total Indebtedness To Gross Assets Value	45.00%
Minimum [Member] | Pricing Level 5 [Member]
Debt Instrument [Line Items]
Ratio of Total Indebtedness To Gross Assets Value	52.50%