XML 79 R63.htm IDEA: XBRL DOCUMENT v3.6.0.2
Fair Value Measurements - Quantitative Information about Level 3 Fair Value (Details) - Option Model - Implied Volatility - Fuel derivatives
Dec. 31, 2016
2017  
Quantitative Information About Level 3 [Line Items]  
Fair Value Measurement Range, Minimum 16.00%
Fair Value Measurement Range, Maximum 36.00%
2018  
Quantitative Information About Level 3 [Line Items]  
Fair Value Measurement Range, Minimum 20.00%
Fair Value Measurement Range, Maximum 31.00%
2019  
Quantitative Information About Level 3 [Line Items]  
Fair Value Measurement Range, Minimum 18.00%
Fair Value Measurement Range, Maximum 24.00%