Capital Stock (Narrative) (Details) - USD ($) $ / shares in Units, shares in Millions	1 Months Ended	2 Months Ended	3 Months Ended								12 Months Ended
	Feb. 09, 2018	Mar. 23, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jan. 30, 2018	Dec. 07, 2017	May 12, 2015
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Dividends Payable, Date Declared			Oct. 24, 2017	Jul. 25, 2017	Apr. 27, 2017	Feb. 22, 2017	Nov. 01, 2016	Jul. 26, 2016	Apr. 26, 2016	Feb. 18, 2016
Share-based compensation expense											$ 169,600,000	$ 164,600,000	$ 148,200,000
Tax benefit from share-based compensation expense											$ 67,800,000	60,500,000	53,700,000
Document Fiscal Year Focus											2017
Cash received from exercise of stock options											$ 225,300,000	119,400,000	186,000,000
Employee stock purchase plan, purchase price per share as a percent of closing price											95.00%
Increase in stock repurchase program authorization															$ 5,000,000,000.0
Accelerated share repurchase program, shares repurchased											10.5
Outstanding principal amount			$ 396,100,000								$ 396,100,000
Dividends Payable, Date to be Paid			Dec. 21, 2017	Sep. 25, 2017	Jun. 23, 2017	Mar. 24, 2017	Dec. 21, 2016	Sep. 26, 2016	Jun. 24, 2016	Mar. 25, 2016
Dividends Payable, Date of Record			Dec. 05, 2017	Sep. 08, 2017	Jun. 09, 2017	Mar. 10, 2017	Dec. 05, 2016	Sep. 09, 2016	Jun. 10, 2016	Mar. 10, 2016
Stock Repurchase Program, Remaining Authorized Repurchase Amount			$ 7,178,100,000								$ 7,178,100,000
Incentive Compensation Plan [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Number of registered shares for issuance			37.5								37.5
Number of shares available for future issuance			29.3								29.3
Restricted Stock Units (RSUs) [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Fair value of shares vested											$ 127,200,000	184,900,000	257,200,000
Approximate number of performance restricted stock units granted											0.4
Unrecognized compensation cost			$ 127,200,000								$ 127,200,000
Weighted-average remaining requisite service period											14 months
Stock Option [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock incentive plan vesting period, years											3 years
Stock option term, years											10 years
Intrinsic value of options exercised											$ 192,300,000	103,000,000	188,100,000
Tax benefit from stock option exercises and disqualifying dispositions											75,900,000	37,900,000	68,000,000
Cash received from exercise of stock options											200,000,000	95,400,000	$ 162,200,000
Unrecognized compensation cost			$ 17,600,000								$ 17,600,000
Weighted-average remaining requisite service period											10 months
Subsequent Event [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Dividends Payable, Amount Per Share														$ 0.7500
Accelerated share repurchase program, shares repurchased	0.7
Dividends Payable, Date to be Paid		Mar. 23, 2018
Dividends Payable, Date of Record		Mar. 09, 2018
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 7,021,500,000
Employee Stock Purchase Plan [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Number of registered shares for issuance			14.0								14.0
Number of shares available for future issuance			5.2								5.2
Maximum amount of stock employees are permitted to purchase per calender year (whole dollars)											$ 25,000
Payroll deductions, percent of gross compensation, minimum			1.00%								1.00%
Payroll deductions, percent of gross compensation, maximum			15.00%								15.00%
Employee stock purchase plan, purchase price per share as a percent of closing price											95.00%
Stock Issued During Period, Shares											0.2
Equity Unit Purchase Agreements [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Equity Units Issued			25.0								25.0					25.0
Outstanding principal amount			$ 1,250,000,000				$ 1,250,000,000				$ 1,250,000,000	$ 1,250,000,000				$ 1,250,000,000