Stockholders' Equity - Changes in accumulated other comprehensive income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Forward-starting Interest Rate Swaps
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ (1,569)	$ 0
Other comprehensive income (loss) before reclassifications	0	(723)
Amounts reclassified from accumulated other comprehensive loss	42	0
Net accumulated other comprehensive income (loss)	42	(723)
Ending balance	(1,527)	(723)
Defined Benefit Pension Plans
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	0	(2,519)
Other comprehensive income (loss) before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive loss	0	0
Net accumulated other comprehensive income (loss)	0	0
Ending balance	$ 0	$ (2,519)