Investments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Oct. 01, 2016	Sep. 30, 2017	Oct. 01, 2016	Dec. 31, 2016
Investments
Unrealized gains (losses) on trading securities	$ 54	$ 27	$ 114	$ 41
Trading securities
Investments
Amortized Cost	1,201		1,201		$ 1,236
Fair Value	1,358		1,358		1,277
Domestic equity securities
Investments
Amortized Cost	609		609		444
Fair Value	716		716		482
Foreign equity securities
Investments
Amortized Cost	265		265		198
Fair Value	310		310		199
Domestic debt securities held in mutual funds/ETFs/U.S. Treasuries
Investments
Amortized Cost	174		174		437
Fair Value	175		175		437
High yield securities
Investments
Amortized Cost	85		85		114
Fair Value	86		86		115
Money market funds held in trading accounts
Investments
Amortized Cost	36		36		13
Fair Value	36		36		13
Collateralized loan obligation
Investments
Amortized Cost	28		28		25
Fair Value	29		29		26
Other trading securities
Investments
Amortized Cost	4		4		5
Fair Value	6		6		5
Denominated in foreign currencies | Money market funds
Investments
Fair Value					1
Denominated in foreign currencies | Money market funds | Maximum
Investments
Fair Value	1		1
Denominated in foreign currencies | Foreign equity securities
Investments
Fair Value	110		110		91
Denominated in Euros | Foreign equity securities
Investments
Fair Value	47		47		35
Denominated in Japanese Yen | Foreign equity securities
Investments
Fair Value	22		22		20
Denominated in British pounds | Foreign equity securities
Investments
Fair Value	19		19		16
Denominated in Swiss Franc | Foreign equity securities
Investments
Fair Value	6		6		6
Denominated in other foreign currencies | Foreign equity securities
Investments
Fair Value	$ 16		$ 16		$ 14