Stockholders' Equity - Changes in accumulated other comprehensive income (Details) - Forward-starting Interest Rate Swaps - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ (1,401)	$ (1,569)
Amounts reclassified from accumulated other comprehensive loss	43	42
Net accumulated other comprehensive income	43	42
Ending balance	$ (1,358)	$ (1,527)