Preferred and Common Stock - Additional Information (Details)		1 Months Ended		3 Months Ended												12 Months Ended
	Oct. 02, 2017 $ / shares shares	Jul. 30, 2015 Tranche	Sep. 30, 2014 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Sep. 30, 2019 $ / shares	Jun. 30, 2019 $ / shares	Mar. 31, 2019 $ / shares	Dec. 31, 2018 USD ($) $ / shares shares	Sep. 30, 2018 $ / shares	Jun. 30, 2018 $ / shares	Mar. 31, 2018 $ / shares	Dec. 31, 2017 USD ($) $ / shares	Sep. 30, 2017 $ / shares	Jun. 30, 2017 $ / shares shares	Mar. 31, 2017 $ / shares	Dec. 31, 2021 USD ($)	Dec. 31, 2019 USD ($) class_of_stock $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 $ / shares	Dec. 31, 2015 $ / shares	Nov. 14, 2019 USD ($)	Nov. 06, 2019 USD ($)	Oct. 15, 2019 USD ($)	Aug. 06, 2019 USD ($)	May 14, 2019 USD ($)	May 02, 2019 USD ($)	Feb. 19, 2019 USD ($)	Dec. 01, 2015 USD ($)
Preferred Stock
Preferred stock, number of classes | class_of_stock																	2
Preferred stock par value (usd per share) | $ / shares			$ 1
Public offering of preferred stock			$ 1,250,000,000
Depository shares sold (in shares) | shares	24,022		25,000,000											12,958,767
Proceeds from public offering			$ 1,213,000,000
Preferred stock conversion rate			0.10
Conversion of stock, shares converted (in shares) | shares	31,420
Common Stock
Common stock, shares authorized (in shares) | shares				600,000,000													600,000,000
Common stock outstanding (in shares) | shares				432,855,183													432,855,183
Common stock, dividends declared per share (usd per share) | $ / shares																	$ 0.12	$ 0.24	$ 0.24
Dividends paid per share (usd per share) | $ / shares				$ 0.02	$ 0.02	$ 0.02	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.06			$ 0.24	$ 0.24
Number of shares available for issuance | shares				47,000,000													47,000,000
Common stock reserved for future issuance (in shares) | shares				37,000,000													37,000,000
Stock-based Compensation
Stock based compensation expense (benefit), before tax																	$ 78,000,000	$ 50,000,000	$ 54,000,000
Stock based compensation expense, after tax																	70,000,000	$ 39,000,000	$ 36,000,000
Share-based payment arrangement included in cash bonus award																	21,000,000
Stock based compensation expense, stock awards percentage																		85.00%	85.00%
Stock-based compensation expense capitalized				$ 0				$ 0				$ 0					0	$ 0	$ 0
Unrecognized compensation costs on non-vested stock option grants (pretax)				50,000,000													$ 50,000,000
Unrecognized compensation costs on non-vested awards, weighted average period of recognition in years																	1 year 3 months 18 days
Share-based compensation arrangement by share-based payment award, options, grants in period, weighted average grant date fair value (in usd per share) | $ / shares																	$ 11.93	$ 9.79	$ 6.26
Average risk-free interest rate. percentage																	1.60%
Number of options, outstanding weighted average remaining contractual life																	3 years 4 months 24 days
Total intrinsic value of options outstanding				$ 40,000,000													$ 40,000,000
Stock options vested (in shares) | shares																	5,900,000
Weighted average remaining contractual life, vested and exercisable																	3 years
Weighted average exercise price, vested and exercisable (in usd per share) | $ / shares				$ 25.80													$ 25.80
Total intrinsic value of options vested and exercisable				$ 36,000,000													$ 36,000,000
Proceeds from exercise of employee stock options																	56,000,000	$ 16,000,000	$ 50,000,000
Total tax benefit realized from these exercises																	4,000,000	2,000,000	4,000,000
Total intrinsic value of options exercised																	17,000,000	$ 7,000,000	13,000,000
Restructuring and Other Charges
Stock-based Compensation
Stock based compensation expense (benefit), before tax																	$ (3,000,000)		$ (13,000,000)
Stock Options
Stock-based Compensation
Stock options granted, vesting period																	3 years
Share-based compensation arrangement by share-based payment award, expiration period																	10 years
Stock options granted, contractual term																	6 months
Average risk-free interest rate. percentage																	2.50%
Volatility, percentage																		34.00%	38.10%
Dividend yield, percentage																	0.90%
Annual pre- and post-vesting forfeitures, percentage																	6.00%
Exercise behavior, percentage																	61.00%
Life (years)																	6 years
Restricted Stock Units (RSUs)
Stock-based Compensation
Stock options granted, contractual term																	3 years
Percentage of remaining share based compensation expenses																	95.00%
Share-based compensation arrangement by share-based payment award, options, grants in period, weighted average grant date fair value (in usd per share) | $ / shares																	$ 20.25	$ 0.027
Volatility, percentage																	33.40%	32.00%
Common stock
Preferred Stock
Conversion of stock, shares converted (in shares) | shares																			39,242,706
Class B Mandatory Convertible Preferred Stock
Preferred Stock
Percentage ownership			5.375%
Mandatory convertible preferred stock
Preferred Stock
Depository shares sold (in shares) | shares	24,975,978
Preferred stock liquidation preference (usd per share) | $ / shares			$ 500
Preferred shares (in shares) | shares			2,500,000
Preferred stock conversion rate	0.1
Preferred stock conversion price (in usd per share) | $ / shares	$ 1.56996
Conversion of stock, shares converted (in shares) | shares	39,211,286
Preferred Class A
Preferred Stock
Number of shares of preferred stock authorized (in shares) | shares				660,000													660,000
Preferred stock par value (usd per share) | $ / shares				$ 100													$ 100
Preferred stock dividend declared (usd per share) | $ / shares																	$ 3.75	$ 3.75	$ 3.75
Preferred stock, shares outstanding | shares				546,024				546,024									546,024	546,024
Preferred Class B
Preferred Stock
Number of shares of preferred stock authorized (in shares) | shares				10,000,000													10,000,000
Preferred stock par value (usd per share) | $ / shares				$ 1													$ 1
Preferred stock dividend declared (usd per share) | $ / shares																	$ 0	$ 0	$ 20.1563	$ 26.8750	$ 26.8750
Preferred stock, shares outstanding | shares								0										0
Cash paid for dividends, preferred stock (per share) | $ / shares																		$ 20.1563
Share-based Compensation Award, Tranche One | Stock Options
Stock-based Compensation
Share-based compensation arrangement by share-based payment award, award vesting rights, percentage																	33.33%
Share-based Compensation Award, Tranche Two | Stock Options
Stock-based Compensation
Share-based compensation arrangement by share-based payment award, award vesting rights, percentage																	33.33%
Share-based Compensation Award, Tranche Three | Stock Options
Stock-based Compensation
Share-based compensation arrangement by share-based payment award, award vesting rights, percentage																	33.33%
Convertible Debt
Common Stock
Number of repayment tranches | Tranche		2
Convertible Debt | Tranche Due December 2015
Common Stock
Debt instrument, face amount																													$ 115,000,000
Convertible Debt | Tranche Due October 2019
Common Stock
Debt instrument, face amount																								$ 403,000,000
February 2019 ASR
Share Activity
Stock repurchase program, authorized amount																												$ 700,000,000
May 2019 ASR
Share Activity
Stock repurchase program, authorized amount																									$ 200,000,000	$ 500,000,000	$ 200,000,000
Share Repurchases Program November 2019
Share Activity
Stock repurchase program, authorized amount																						$ 50,000,000
Accelerated Share Repurchase Program
Share Activity
Stock repurchase program, remaining repurchase amount																							$ 350,000,000
Scenario, Forecast
Stock-based Compensation
Cash payments for performance awards																$ 23,000,000