Related Party Transactions (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Related Party Transaction [Line Items]
Management fee	$ 6,508	$ 6,877
ACM
Related Party Transaction [Line Items]
Automatic renewal period of management agreement	5 years
Period of written notice of termination	180 days
Management fee	$ 6,508	6,877
ACM | Other Expense
Related Party Transaction [Line Items]
Management fee	467	382
ACM | Stock Based Compensation Expense
Related Party Transaction [Line Items]
Management fee	$ 118	$ 179