Consolidated Statement of Changes in Equity - USD ($) shares in Millions, $ in Millions	Total	Common stock	Additional paid-in capital	Treasury stock	Accumulated other comprehensive income	Retained earnings
Beginning balance at Dec. 31, 2016					$ (1,497.6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 615.3
Other comprehensive income (loss), net of tax	1,697.7
Dividends						$ (234.7)
Ending balance at Jun. 30, 2017					200.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative-effect adjustment | ASU 2014-09	52.0					52.0
Cumulative-effect adjustment | ASU 2016-01	67.9					67.9
Cumulative-effect adjustment | ASU 2016-06	7.5					7.5
Beginning balance at Dec. 31, 2017	$ 36,176.4	$ 81.6	$ 25,082.2	$ (283.0)	1,375.0	9,920.6
Beginning balance (in shares) at Dec. 31, 2017	917.1	917.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 1,166.1
Other comprehensive income (loss), net of tax	(647.4)				(647.4)
Shares issued under employee benefit plans and other (in shares)		4.3
Shares issued under employee benefit plans and other	127.6	$ 0.3	127.3
Share-based compensation	86.9		86.9
Shares released by employee benefit trust to satisfy exercise of stock options				7.9		(7.9)
Dividends	(276.6)					(276.6)
Ending balance at Jun. 30, 2018	$ 36,760.4	$ 81.9	$ 25,296.4	$ (275.1)	$ 727.6	$ 10,929.6
Ending balance (in shares) at Jun. 30, 2018	921.4	921.4