Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Net revenues	$ 2,381	$ 1,512	$ 1,641	$ 1,965	$ 2,043	$ 1,618	$ 1,631	$ 1,726	$ 7,500	$ 7,017	$ 6,608
Cost of revenues	832	513	510	662	803	552	561	585
Operating income	694	265	434	595	221	257	339	493	1,988	1,309	1,412
Net income	$ 650	$ 260	$ 402	$ 500	$ (584)	$ 188	$ 243	$ 426	$ 1,813	$ 273	$ 966
Basic earnings per common share (in dollars per share)	$ 0.85	$ 0.34	$ 0.53	$ 0.66	$ (0.77)	$ 0.25	$ 0.32	$ 0.57	$ 2.38	$ 0.36	$ 1.30
Diluted earnings per common share (in dollars per share)	$ 0.84	$ 0.34	$ 0.52	$ 0.65	$ (0.77)	$ 0.25	$ 0.32	$ 0.56	$ 2.35	$ 0.36	$ 1.28