Preferred and Common Stock - Additional Information (Detail)						1 Months Ended					3 Months Ended											12 Months Ended			14 Months Ended
	Oct. 02, 2017 $ / shares shares	Oct. 05, 2016 $ / shares shares	Aug. 31, 2016 shares	Jul. 23, 2015 shares	Jul. 22, 2015 shares	Aug. 31, 2016 shares	Aug. 31, 2016 USD ($) shares	Aug. 30, 2016 USD ($)	Jul. 31, 2015 USD ($) $ / shares shares	Sep. 30, 2014 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	Sep. 30, 2017 $ / shares	Jun. 30, 2017 $ / shares shares	Mar. 31, 2017 $ / shares	Dec. 31, 2016 USD ($) $ / shares shares	Sep. 30, 2016 $ / shares	Jun. 30, 2016 $ / shares	Mar. 31, 2016 $ / shares	Sep. 30, 2015 $ / shares	Jun. 30, 2015 $ / shares	Mar. 31, 2015 $ / shares	Dec. 31, 2017 USD ($) class_of_stock $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Oct. 04, 2016 shares	Dec. 31, 2014 shares
Class of Stock [Line Items]
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
Interest in preferred stock	0.10									0.10
Conversion of stock, shares converted (in shares) | shares	31,420
Reverse stock split ratio		0.3333
Common stock outstanding (in shares) | shares		400,000,000									481,416,537				438,519,780							481,416,537	438,519,780	1,310,160,141	1,300,000,000.0	1,216,663,661
Common stock, par value per share (usd pe share) | $ / shares		$ 1
Common stock decrease																							$ 877,000,000
Additional capital increase (decrease)																							877,000,000
Common stock authorized (in shares) | shares		600,000,000																							1,800,000,000
Treasury stock retirement (in shares) | shares			25,000,000			76,000,000	76,000,000
Retirement of treasury stock								$ 76,000,000															0
Treasury stock, value											$ 0				$ 0							$ 0	$ 0
Common stock issued (in shares) | shares											481,416,537											481,416,537
Dividends paid per share (usd per share) | $ / shares											$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.09	$ 0.09	$ 0.09	$ 0.09	$ 0.09	$ 0.09	$ 0.09			$ 0.36
Common stock, dividends yield (usd per share) | $ / shares											$ 0.06											$ 0.24	$ 0.36	$ 0.12
Document Fiscal Year Focus																						2017
Common stock reserved for future issuance (in shares) | shares											47,000,000											47,000,000
Common stock, number of shares available for grant | shares											43,000,000											43,000,000
Stock based compensation expense, before tax																						$ 54,000,000	$ 76,000,000	$ 77,000,000
Stock based compensation expense, after tax																						$ 36,000,000	$ 51,000,000	$ 51,000,000
Stock based compensation expense, stock awards percentage																						85.00%	80.00%	80.00%
Unrecognized compensation costs on non-vested stock option awards (pretax)											$ 0				$ 0							$ 0	$ 0	$ 0
Unrecognized compensation costs on non-vested stock option grants (pretax)											43,000,000											$ 43,000,000
Unrecognized compensation costs on non-vested awards, weighted average period of recognition in years																						1 year 7 months 6 days
Expense related to the acceleration of expense related to retirement-eligible employees																						$ 15,000,000	$ 19,000,000	$ 15,000,000
Weighted average FMV per award, Granted (in usd per share) | $ / shares																						$ 21.86
Average risk-free interest rate																						2.40%
Share-based compensation arrangement by share-based payment award, options, grants in period, weighted average grant date fair value | $ / shares																						$ 6.26	$ 4.78	$ 10.07
Volatility																						38.10%	44.50%	36.50%
Dividend yield																						1.20%
Annual pre- and post-vesting forfeitures																						6.00%
Exercise behavior																						59.00%
Life (years)																						5 years 10 months 24 days
Number of options, Outstanding weighted average remaining contractual life																						5 years 3 months 29 days
Total intrinsic value of options outstanding											$ 53,000,000											$ 53,000,000
Stock options vested (in shares) | shares																						7,400,000
Stock option exercisable | shares																						8,900,000
Weighted average remaining contractual life, vested and exercisable																						4 years 1 month 28 days
Weighted average exercise price, vested and exercisable (in usd per share) | $ / shares											$ 25.90											$ 25.90
Total intrinsic value of options vested and exercisable											$ 26,000,000											$ 26,000,000
Proceeds from exercise of employee stock options																						50,000,000	$ 4,000,000	$ 25,000,000
Total tax benefit realized from these exercises																						4,000,000	0	6,000,000
Total intrinsic value of options exercised																						13,000,000	1,000,000	19,000,000
Restructuring and Other Charges
Class of Stock [Line Items]
Stock based compensation expense, before tax																						$ (13,000,000)
Stock Options
Class of Stock [Line Items]
Stock options granted, vesting period																						3 years
Share-based compensation arrangement by share-based payment award, expiration period																						10 years
Stock option exercisable | shares																						2,000,000
Restricted Stock Units (RSUs)
Class of Stock [Line Items]
Stock options granted, contractual term																						3 years
Share-based compensation arrangement by share-based payment award, award performance period																						3 years
Performance Shares
Class of Stock [Line Items]
Share-based compensation arrangement by share-based payment award, award performance period																						3 years
Weighted average FMV per award, Granted (in usd per share) | $ / shares																						$ 21.99
Average risk-free interest rate																						1.50%
Volatility																						38.00%
RTI
Class of Stock [Line Items]
Number of common stock shares issued in a part of acquisition (in shares) | shares		29,000,000		87,397,414	29,132,471				29,132,471																87,000,000
Number of shares to be issued upon conversion | $ / shares											$ 14,294,000											$ 14,294,000
Debt instrument, convertible, conversion price | $ / shares									$ 2.8315
RTI | Convertible Notes
Class of Stock [Line Items]
Debt instrument, convertible, conversion price | $ / shares									$ 28.1596
Debt instrument, amount received upon maturity per one thousand dollars in principal amount of notes held									$ 1,000
RTI | Tranche Due December 2015
Class of Stock [Line Items]
Long-term debt due within one year									115,000,000
RTI | Tranche Due October 2019
Class of Stock [Line Items]
Long-term debt due within one year									$ 403,000,000															$ 403,000,000
RTI | 1.63% Convertible Notes, Due 2019 | Convertible Notes
Class of Stock [Line Items]
Debt instrument, convertible, conversion rate per bond											0.0355119											0.0355119
Debt instrument, convertible, conversion price | $ / shares											$ 28.1596											$ 28.1596
Common stock
Class of Stock [Line Items]
Retirement of treasury stock							$ 76,000,000	76,000,000															76,000,000
Number of common stock shares issued in a part of acquisition (in shares) | shares																								87,397,414
Additional capital
Class of Stock [Line Items]
Retirement of treasury stock							$ 2,563,000,000	$ 2,563,000,000															$ 2,563,000,000
Class B Mandatory Convertible Preferred Stock
Class of Stock [Line Items]
Percentage ownership										5.375%
Mandatory convertible preferred stock
Class of Stock [Line Items]
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
Interest in preferred stock	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
Class of Stock [Line Items]
Preferred stock, shares 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 (in shares) | shares											546,024				546,024							546,024	546,024
Preferred Class B
Class of Stock [Line Items]
Preferred stock, shares 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																						$ 20.1563	$ 26.875	$ 26.8750
Preferred stock, shares outstanding (in shares) | shares											0				2,500,000							0	2,500,000
Preferred stock, dividends, per share, cash paid | $ / shares																						$ 20.1563
Share-based Compensation Award, Tranche One | Stock Options
Class of Stock [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting rights, percentage																						33.33%
Share-based Compensation Award, Tranche Two | Stock Options
Class of Stock [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting rights, percentage																						33.33%
Share-based Compensation Award, Tranche Three | Stock Options
Class of Stock [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting rights, percentage																						33.33%
Twenty Seventeen Awards | Performance Shares
Class of Stock [Line Items]
Stock options granted, vesting period																						3 years
Twenty Fifteen And Twenty Sixteen Awards | Share-based Compensation Award, Tranche One | Performance Shares
Class of Stock [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting rights, percentage																						33.33%
Twenty Fifteen And Twenty Sixteen Awards | Share-based Compensation Award, Tranche Two | Performance Shares
Class of Stock [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting rights, percentage																						33.33%
Twenty Fifteen And Twenty Sixteen Awards | Share-based Compensation Award, Tranche Three | Performance Shares
Class of Stock [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting rights, percentage																						33.33%