Securities Financing Activities - Gross and Net Amounts of Securities Financing Agreements (Details) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Assets
Securities purchased under resale agreements, Gross amounts	$ 758,505,000,000	$ 691,116,000,000
Securities purchased under resale agreements, Amounts netted on the Consolidated balance sheets	(459,365,000,000)	(369,612,000,000)
Securities purchased under resale agreements, Amounts presented on the Consolidated balance sheets	299,140,000,000	321,504,000,000
Securities purchased under resale agreements, Amounts not nettable on the Consolidated balance sheets	(284,790,000,000)	(308,854,000,000)
Securities purchased under resale agreements, Net amounts	14,350,000,000	12,650,000,000
Securities borrowed, Gross amounts	147,066,000,000	132,955,000,000
Securities borrowed, Amounts netted on the Consolidated balance sheets	(23,880,000,000)	(20,960,000,000)
Securities borrowed, Amounts presented on the Consolidated balance sheets	123,186,000,000	111,995,000,000
Securities borrowed, Amounts not nettable on the Consolidated balance sheets	(86,241,000,000)	(79,747,000,000)
Securities borrowed, Net amounts	36,945,000,000	32,248,000,000
Liabilities
Securities sold under repurchase agreements, Gross amounts	667,703,000,000	541,587,000,000
Securities sold under repurchase agreements, Amounts netted on the Consolidated balance sheets	(459,365,000,000)	(369,612,000,000)
Securities sold under repurchase agreements, Amounts presented on the Consolidated balance sheets	208,338,000,000	171,975,000,000
Securities sold under repurchase agreements, Amounts not nettable on the Consolidated balance sheets	(190,697,000,000)	(149,125,000,000)
Securities sold under repurchase agreements, Net amounts	17,641,000,000	22,850,000,000
Securities loaned and other, Gross amounts	40,722,000,000	33,700,000,000
Securities loaned and other, Amounts netted on the Consolidated balance sheets	(23,880,000,000)	(20,960,000,000)
Securities loaned and other, Amounts presented on the Consolidated balance sheets	16,842,000,000	12,740,000,000
Securities loaned and other, Amounts not nettable on the Consolidated balance sheets	(16,732,000,000)	(12,358,000,000)
Securities loaned and other, Net amounts	110,000,000	382,000,000
Securities purchased under resale agreements where an appropriate legal opinion has not been either sought or obtained, Gross asset balance	8,200,000,000	7,900,000,000
Securities borrowed where an appropriate legal opinion has not been either sought or obtained	34,500,000,000	30,300,000,000
Securities sold under agreements to repurchase	15,900,000,000	21,500,000,000
Securities loaned and other	46,000,000	25,000,000
Securities-for-securities
Liabilities
Securities loaned and other, Amounts presented on the Consolidated balance sheets	3,300,000,000	3,300,000,000
Securities financing agreements accounted for at fair value
Assets
Securities purchased under resale agreements, Amounts presented on the Consolidated balance sheets	14,000,000,000.0	13,200,000,000
Liabilities
Securities sold under repurchase agreements, Amounts presented on the Consolidated balance sheets	971,000,000	935,000,000
Securities borrowed, fair value	5,600,000,000	5,100,000,000
Securities financing agreements accounted for at fair value | Securities loaned
Liabilities
Securities loaned accounted for at fair value	$ 0	$ 0