Shareholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended			9 Months Ended		12 Months Ended
	Oct. 13, 2020	Oct. 06, 2020	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Equity [Line Items]
Common stock, shares authorized			4,000,000,000.00			4,000,000,000.00		4,000,000,000.00
Nonvoting common stock, shares authorized			200,000,000			200,000,000		200,000,000
Nonvoting common stock, par value			$ 0.01			$ 0.01		$ 0.01
Shares remitted by employees to satisfy minimum statutory employee tax withholding						3,476
Remitted Shares, Total						$ 0.9
Amount of share-based awards cancelled to satisfy minimum statutory employee tax withholding requirements						3,400,000
Value of share-based awards cancelled to satisfy minimum statutory employee tax withholding requirements						$ 828.0
Dividends declared per common share			1.25		$ 1.25	$ 3.75	$ 2.90
Subsequent Event [Member]
Equity [Line Items]
Dividends declared per common share	$ 1.25
Dividends payable date declared	Oct. 13, 2020
Dividends payable date to be paid	Dec. 30, 2020
Dividends payable date of record	Dec. 02, 2020
Series B Preferred Stock [Member]
Equity [Line Items]
Number of shares redeemed								6,000
Dividend rate								6.20%
Amount of redeemed								$ 150.0
Preferred Stock, Redemption Price Per Share								$ 25,000
Difference between the redemption value of Preferred Stock and the net carrying value at the time of redemption							$ 7.0	$ 9.0
Preferred stock dividends declared							$ 775.00
Series A Preferred Stock [Member]
Equity [Line Items]
Preferred stock dividends declared			236.98		244.79	708.34	708.34
Series A Preferred Stock [Member] | Subsequent Event [Member] | Group Inc. [Member]
Equity [Line Items]
Preferred stock dividends declared		$ 239.58
Series C Preferred Stock [Member]
Equity [Line Items]
Preferred stock dividends declared			252.78		261.11	755.56	755.55
Series C Preferred Stock [Member] | Subsequent Event [Member] | Group Inc. [Member]
Equity [Line Items]
Preferred stock dividends declared		255.56
Series D Preferred Stock [Member]
Equity [Line Items]
Preferred stock dividends declared			252.78		261.11	755.56	755.55
Series D Preferred Stock [Member] | Subsequent Event [Member] | Group Inc. [Member]
Equity [Line Items]
Preferred stock dividends declared		255.56
Series J Preferred Stock [Member]
Equity [Line Items]
Preferred stock dividends declared			343.75		343.75	1,031.25	1,031.25
Series J Preferred Stock [Member] | Subsequent Event [Member] | Group Inc. [Member]
Equity [Line Items]
Preferred stock dividends declared		343.75
Series K Preferred Stock [Member]
Equity [Line Items]
Preferred stock dividends declared			398.44		398.44	1,195.32	1,195.32
Series K Preferred Stock [Member] | Subsequent Event [Member] | Group Inc. [Member]
Equity [Line Items]
Preferred stock dividends declared		398.44
Series L Preferred Stock [Member]
Equity [Line Items]
Number of shares redeemed				14,000				38,000
Dividend rate				5.70%
Amount of redeemed				$ 350.0				$ 950.0
Preferred Stock, Redemption Price Per Share				$ 25,000				$ 25,000
Difference between the redemption value of Preferred Stock and the net carrying value at the time of redemption				$ 1.0
Preferred stock dividends declared					419.68	361.54	1,132.18
Series M Preferred Stock [Member]
Equity [Line Items]
Preferred stock dividends declared			279.17			951.05	671.88
Series M Preferred Stock [Member] | Subsequent Event [Member] | Group Inc. [Member]
Equity [Line Items]
Preferred stock dividends declared		266.11
Series N Preferred Stock [Member]
Equity [Line Items]
Preferred stock dividends declared			393.75		393.75	1,181.25	1,181.25
Series N Preferred Stock [Member] | Subsequent Event [Member] | Group Inc. [Member]
Equity [Line Items]
Preferred stock dividends declared		393.75
Series O Preferred Stock [Member]
Equity [Line Items]
Preferred stock dividends declared						662.50	662.50
Series O Preferred Stock [Member] | Subsequent Event [Member] | Group Inc. [Member]
Equity [Line Items]
Preferred stock dividends declared		662.50
Series P Preferred Stock [Member]
Equity [Line Items]
Preferred stock dividends declared						625.00	625.00
Series P Preferred Stock [Member] | Subsequent Event [Member] | Group Inc. [Member]
Equity [Line Items]
Preferred stock dividends declared		625.00
Series E Preferred Stock [Member]
Equity [Line Items]
Preferred stock dividends declared			1,022.22		1,022.22	3,044.44	3,044.44
Series E Preferred Stock [Member] | Subsequent Event [Member] | Group Inc. [Member]
Equity [Line Items]
Preferred stock dividends declared		1,011.11
Series F Preferred Stock [Member]
Equity [Line Items]
Preferred stock dividends declared			1,022.22		$ 1,022.22	$ 3,044.44	$ 3,044.44
Series F Preferred Stock [Member] | Subsequent Event [Member] | Group Inc. [Member]
Equity [Line Items]
Preferred stock dividends declared		$ 1,011.11
Series S Preferred Stock [Member]
Equity [Line Items]
Dividend rate						4.40%
Preferred stock dividends declared			$ 586.67			$ 586.67
Preferred stock shares issued						14,000