Financial Instruments and Fair Values - Effect of Derivative Financial Instruments Designated as Cash Flow Hedges (Details) - Designated as Hedging Instrument - Cash Flow Hedging - Interest Rate Swap - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in other comprehensive income (loss) - effective portion	$ (14,367)	$ (10,864)	$ (12,973)	$ (30,235)
Amount of gain (loss) reclassified from accumulated other comprehensive income (loss) into interest expense - effective portion	(43)	0	(43)	0
Amount of gain (loss) recognized in other expense - ineffective portion	$ (42)	$ 0	$ (289)	$ 0