Nature of Operations and Significant Accounting Policies - Restructuring Charges (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 25, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring Charge	$ 173	$ 0
Management Streamlining Initiative
Restructuring Cost and Reserve [Line Items]
Restructuring Charge	173	0
Management Streamlining Initiative | Severance and Pension
Restructuring Cost and Reserve [Line Items]
Restructuring Charge	131	0
Management Streamlining Initiative | Other Post-retirement Benefits Curtailment
Restructuring Cost and Reserve [Line Items]
Restructuring Charge	13	0
Management Streamlining Initiative | Executive Equity Awards Proration
Restructuring Cost and Reserve [Line Items]
Restructuring Charge	11	0
Management Streamlining Initiative | Management Workforce Reduction
Restructuring Cost and Reserve [Line Items]
Restructuring Charge	155	0
Management Streamlining Initiative | Executive Equity Awards Proration
Restructuring Cost and Reserve [Line Items]
Restructuring Charge	8	0
Management Streamlining Initiative | Advisory Fees Related to Shareholder Matters
Restructuring Cost and Reserve [Line Items]
Restructuring Charge	$ 10	$ 0