Capital Stock - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions				1 Months Ended			12 Months Ended
	May 01, 2024	Mar. 31, 2019	May 01, 2014	Oct. 31, 2019	Jul. 31, 2019	Apr. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Incentive Plans
Number of shares repurchased (in shares)							25,500,000	38,500,000	5,000,000.0
Cost of shares repurchased							$ 488.5	$ 904.1	$ 123.7
Cumulative number of shares repurchased under a share repurchase program (in shares)							99,000,000.0
Treasury stock, cumulative shares retired (in shares)							20,000,000.0
Cumulative cost of shares repurchased under a share repurchase program							$ 1,900.0
Treasury stock reissued (in shares)							0
Increase in shares authorized (in shares)					25,000,000.0
Shares held as treasury stock (in shares)							79,000,000.0	53,409,705
Treasury stock, number of shares authorized to be repurchased (in shares)							11,000,000.0
Cash dividends, per share (in dollars per share)		$ 0.07		$ 0.10		$ 0.09	$ 0.35	$ 0.25	$ 0.17
2014 Incentive Plan
Incentive Plans
Number of shares reserved for issuance (in shares)			18,000,000.0
Number of shares available for issuance (in shares)							12,800,000
2014 Incentive Plan | Stock Options | Maximum
Incentive Plans
Number of shares reserved for issuance (in shares)			10,000,000.0
2004 Incentive Plan
Incentive Plans
Additional awards granted (in shares)			0
Scenario Forecast | 2014 Incentive Plan
Incentive Plans
Additional awards granted (in shares)	0