Related Party Transactions and Arrangements - Indirect Affiliate Expenses (Details) - Affiliates of Former Manager [Member] - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Related Party Transaction [Line Items]
Related party expenses			$ 8,500,000
Indirect Affiliate Expenses [Member]
Related Party Transaction [Line Items]
Related party expenses	$ 0	$ 0	10,975,000
Audrain building [Member] | Indirect Affiliate Expenses [Member]
Related Party Transaction [Line Items]
Related party expenses			8,724,000
ANST office build-out [Member] | Indirect Affiliate Expenses [Member]
Related Party Transaction [Line Items]
Related party expenses			462,000
New York office [Member] | Indirect Affiliate Expenses [Member]
Related Party Transaction [Line Items]
Related party expenses			1,659,000
Dresher, PA office [Member] | Indirect Affiliate Expenses [Member]
Related Party Transaction [Line Items]
Related party expenses			92,000
North Carolina office [Member] | Indirect Affiliate Expenses [Member]
Related Party Transaction [Line Items]
Related party expenses			$ 38,000