Related Party Transactions and Arrangements (Related Party Fees and Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Affiliates of Former Manager [Member] | Tenant Improvement And Furniture Costs [Member]
Related Party Transaction [Line Items]
Related party expenses		$ 4,700		$ 8,500	$ 8,500
Affiliates of Former Manager [Member] | Indirect Affiliate Expenses [Member]
Related Party Transaction [Line Items]
Related party expenses	$ 0	5,595	$ 0	10,090
Affiliated Entity [Member] | Offering Related Costs [Member]
Related Party Transaction [Line Items]
Related party expenses	0	0	0	2,150
Affiliated Entity [Member] | Acquisition Related Expenses [Member]
Related Party Transaction [Line Items]
Related party expenses	0	0	0	1,652
Affiliated Entity [Member] | Merger And Other Non-Routine Transactions [Member]
Related Party Transaction [Line Items]
Related party expenses	0	0	0	137,778
Affiliated Entity [Member] | Management Fees To Affiliates [Member]
Related Party Transaction [Line Items]
Related party expenses	0	0	0	13,888
Affiliated Entity [Member] | General and Administrative Expense [Member]
Related Party Transaction [Line Items]
Related party expenses	0	60	0	16,089
Affiliated Entity [Member] | Indirect Affiliate Expenses [Member]
Related Party Transaction [Line Items]
Related party expenses	0	5,595	0	10,090
Affiliated Entity [Member] | Total Expenses and Capitalized Costs [Member]
Related Party Transaction [Line Items]
Related party expenses	$ 0	$ 5,655	$ 0	$ 181,647