Capital Stock (Narrative) (Details) - USD ($)	1 Months Ended	3 Months Ended		12 Months Ended
	Oct. 31, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jan. 31, 2016	Sep. 30, 2015
Class of Stock [Line Items]
Stock repurchase program, authorized amount			$ 1,500,000,000.0	$ 6,300,000,000				$ 500,000,000
Available to repurchase common stock				32,700,000
Amount expended on share repurchases in open market transactions				755,704,000	$ 1,640,885,000	$ 406,326,000
Payments for Repurchase of Common Stock				$ 755,704,000	$ 1,640,885,000	$ 406,326,000
Total tax withholdings for share-based compensation (in shares)				679,694	560,239	444,657
Total tax withholdings for share-based compensation				$ 46,336,000	$ 33,672,000	$ 31,013,000
Preferred stock, shares authorized				5,000,000	5,000,000
Preferred stock, par value (in dollars per share)				$ 0.01	$ 0.01
Privately Negotiated Transaction [Member]
Class of Stock [Line Items]
Number of shares repurchased			1,700,000
Payments for Repurchase of Common Stock			$ 101,000,000
Purchase From Accelerated Share Repurchase [Member]
Class of Stock [Line Items]
Number of shares repurchased	2,600,000		21,800,000
Shares repurchased under the ASR		$ 1,400,000,000	$ 1,400,000,000
Open Market Purchases [Member]
Class of Stock [Line Items]
Amount expended on share repurchases in open market transactions				$ 755,700,000	$ 139,900,000	$ 406,300,000
Number of shares repurchased				10,716,850	2,046,400	6,563,986
Average per share price on share repurchases in open market transactions (in dollars per share)				$ 70.52	$ 68.36	$ 61.90
Subsequent Event [Member]
Class of Stock [Line Items]
Stock repurchase program, authorized amount							$ 400,000,000