Fair Value Measurements and Derivative Instruments - Offsetting of Derivative Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Offsetting of Financial Assets under Master Netting Agreements [Abstract]
Gross Amount of Derivative Assets Presented in the Consolidated Balance Sheet	$ 16,297	$ 19,397
Gross Amount of Eligible Offsetting Recognized Derivative Liabilities	(16,297)	(19,397)
Net Amount of Derivative Assets	0	0
Offsetting of Financial Liabilities under Master Netting Agreements [Abstract]
Gross Amount of Derivative Liabilities Presented in the Consolidated Balance Sheet	(357,973)	(373,497)
Gross Amount of Eligible Offsetting Recognized Derivative Assets	16,297	19,397
Cash Collateral Pledged	8,516	7,213
Net Amount of Derivative Liabilities	$ (333,160)	$ (346,887)