Derivative Financial Instruments Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2017		Dec. 31, 2016
Fair value of derivative assets and liabilities
Derivative, Fair Value, Net	$ 61,900		$ (91,700)
Derivative asset current	85,962		54,521
Derivative asset noncurrent	82,194		67,575
Derivative Asset, Fair Value, Gross Asset	168,156		122,096
Derivative liability current	36,296		115,464
Derivatives liability noncurrent	69,915		98,340
Derivative Liability, Fair Value, Gross Liability	106,211		213,804
Derivatives not designated as hedging instruments
Fair value of derivative assets and liabilities
Derivative asset current	85,962		54,521
Derivative asset noncurrent	82,194		67,575
Derivative liability current	36,296		115,464
Derivatives liability noncurrent	69,915		98,340
Fair Value, Inputs, Level 2 [Member] | Derivatives not designated as hedging instruments | Fair Value, Measurements, Recurring [Member]
Fair value of derivative assets and liabilities
Derivative Asset, Fair Value, Gross Asset	168,156	[1]	122,096	[2]
Derivative Liability, Fair Value, Gross Liability	$ 106,211	[1]	$ 213,804	[2]

[1] This represents a financial asset or liability that is measured at fair value on a recurring basis.

[2] This represents a financial asset or liability that is measured at fair value on a recurring basis.