Fair Value of Financial Instruments - Assets and Liabilities at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Assets:
Derivative financial instruments, asset	$ 1,991	$ 1,529
Liabilities:
Derivative financial instrument, liability	742	1,089
Fair Value, Measurements, Recurring
Assets:
Derivative financial instruments, asset	1,991	1,529
Liabilities:
Derivative financial instrument, liability	742	1,089
Fair Value, Measurements, Recurring | Level 1
Assets:
Derivative financial instruments, asset	0	0
Liabilities:
Derivative financial instrument, liability	0	0
Fair Value, Measurements, Recurring | Level 2
Assets:
Derivative financial instruments, asset	1,991	1,529
Liabilities:
Derivative financial instrument, liability	742	1,089
Fair Value, Measurements, Recurring | Level 3
Assets:
Derivative financial instruments, asset	0	0
Liabilities:
Derivative financial instrument, liability	$ 0	$ 0