Fair Value Measurement - Quantitative Information Related to Significant Unobservable Inputs Utilized to Calculate Fair Value (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Derivative asset	$ 48,186	$ 4,464
Derivative liability	(13,848)	$ (12,968)
Level 3 | Derivative Financial Instruments, Liabilities | Discounted Cash Flow
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Derivative liability	$ (7,802)
Range/Input Value	4.37%
Level 3 | Derivative Financial Instruments, Assets | Monte Carlo Simulation Method
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Derivative asset	$ 42,140
Range/Input Value	5.07%