Long-term Debt (Tables)

12 Months Ended

Dec. 31, 2015

Debt Disclosure [Abstract]

Schedule of Long-term Debt Instruments

(in millions)	December 31, 2015		December 31, 2014
5.75% Notes due 2016	$	307	$	313
5.25% Convertible Senior Notes due 2016	111		113
5.125% Notes due 2017	309		316
French Credit Agreements due 2018—1.53%	25		36
Fixed-rate 737 Aircraft Notes payable through 2018—7.02%	17		24
2.75% Notes due 2019	303		300
Term Loan Agreement due 2019—6.315%	143		178
Term Loan Agreement due 2019—4.84%	36		73
2.65% Notes due 2020	494		—
Term Loan Agreement due 2020—5.223%	329		372
Floating-rate 737 Aircraft Notes payable through 2020	257		300
Pass Through Certificates due 2022—6.24%	340		355
7.375% Debentures due 2027	132		134
Capital leases	395		199
	$	3,198	$	2,713
Less current maturities	637		258
Less debt discount and issuance costs	20		21
	$	2,541	$	2,434