Fair Value of Financial Instruments - Fair vlaue of financial assets and liabilities (Details) $ in Thousands	Dec. 31, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 derivative
Fair value of assets and liabilities that are measured on a recurring basis
Assets
Marketable securities	$ 12,065	$ 10,327
Fair value of assets and liabilities that are measured on a recurring basis | Fair Value, Inputs, Level 2
Assets
Derivatives	3,979	7,823
Liabilities
Derivatives	$ 8,353	$ 11,137
Interest Rate Swap
Fair value of assets and liabilities measured on a recurring basis
Number of interest rate derivatives held | derivative			5