Stockholders' Equity - Changes in accumulated other comprehensive income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Bond amortization period			10 years
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Amounts reclassified from accumulated other comprehensive loss arising from loss on defined benefit pension plan	$ 0	$ 0	$ 2,519	$ 0
Forward-starting Interest Rate Swaps
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance			0	0
Other comprehensive income (loss) before reclassifications			(1,684)	0
Amounts reclassified from accumulated other comprehensive loss arising from loss on defined benefit pension plan			0	0
Amounts reclassified from accumulated other comprehensive loss			73	0
Net accumulated other comprehensive income (loss)			(1,611)	0
Ending balance	(1,611)	0	(1,611)	0
Defined Benefit Pension Plans
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance			(2,519)	51
Other comprehensive income (loss) before reclassifications			0	0
Amounts reclassified from accumulated other comprehensive loss arising from loss on defined benefit pension plan			2,519	0
Amounts reclassified from accumulated other comprehensive loss			0	0
Net accumulated other comprehensive income (loss)			2,519	0
Ending balance	$ 0	$ 51	$ 0	$ 51