Retirement Plans - Reconciliation for fair value measurements that use significant unobservable inputs (Details) - Unobservable Inputs Level 3 - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Jan. 02, 2016
Reconciliation for fair value measurements that use significant unobservable inputs (Level 3)
Balance at beginning of year	$ 436
Balance at end of year	494	$ 436
Real estate
Reconciliation for fair value measurements that use significant unobservable inputs (Level 3)
Balance at beginning of year	436	436
Unrealized gains, net	6	46
Realized gains (losses), net	10	(17)
Purchases, sales and settlements, net	42	(29)
Balance at end of year	$ 494	$ 436