Consolidated Statement of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Deferred taxes on unrealized gain (loss), other, tax effect	$ 0	$ 0	$ 7
Deferred taxes on postretirement	(7)	(8)	15
Fuel derivatives
Deferred taxes on unrealized gain (loss) on derivatives, tax effect	(181)	(430)	31
Interest rate derivatives
Deferred taxes on unrealized gain (loss) on derivatives, tax effect	$ 6	$ 5	$ 19