Earnings Per Share - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Thousands	1 Months Ended	3 Months Ended
	May 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Treasury shares acquired (in shares)			1,300
Treasury stock value			$ 220,000,000
Proceeds from Issuance of Common Stock	$ 2,400,000,000
Common Stock [Member]
Class of Stock [Line Items]
Stock Issued During Period, Shares, New Issues	14,025
Gross Proceeds From Issuance Of Equity	$ 2,500,000,000
Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Ownership Interest, Percentage		5.00%
Stock Issued During Period, Shares, New Issues	2,475
Gross Proceeds From Issuance Of Equity	$ 2,500,000,000
Proceeds from Issuance of Preferred Stock and Preference Stock	$ 2,400,000,000
Preferred Stock, Dividend Rate, Percentage		6.125%
Preferred Stock, Liquidation Preference Per Share		$ 1,000
Depositary Share Liquidation Preference		$ 50
Minimum
Class of Stock [Line Items]
Convertible Preferred Stock, Shares Issued upon Conversion		11,700
Maximum
Class of Stock [Line Items]
Convertible Preferred Stock, Shares Issued upon Conversion		14,000