Summary of Significant Accounting Policies - Components of other operating income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other Operating Income [Abstract]
Property lease guaranty revenue	$ 3,890	$ 4,430	$ 5,114
Interest income	579	731	457
Management fee income	370	289	164
Other	208	215	191
Other operating	$ 5,047	$ 5,665	$ 5,926