Long-Term Debt (Long-Term Debt) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012
Debt Instrument [Line Items]
Long-term debt	$ 9,699		$ 7,429
Long-term capital leases	788		706
Increase in carrying value of long-term debt	(35)		174
Floating-rate subordinated notes due to State Street Capital Trust IV in 2037
Debt Instrument [Line Items]
Long-term debt	800		800
Floating-rate subordinated notes due to State Street Capital Trust I in 2028
Debt Instrument [Line Items]
Long-term debt	155		155
2.875% notes due 2016
Debt Instrument [Line Items]
Long-term debt	1,010	[1]	1,014	[1]
3.70% senior notes due in 2023
Debt Instrument [Line Items]
Long-term debt	974	[1]	0	[1]
3.10% subordinated notes due 2023
Debt Instrument [Line Items]
Long-term debt	918	[1]	0	[1]
4.375% notes due 2021
Debt Instrument [Line Items]
Long-term debt	727	[1]	780	[1]
4.956% junior subordinated debentures due 2018
Debt Instrument [Line Items]
Long-term debt	537	[1]	550	[1]
4.30% notes due 2014
Debt Instrument [Line Items]
Long-term debt	502		507
1.35% senior notes due 2018
Debt Instrument [Line Items]
Long-term debt	487	[1]	0	[1]
5.375% notes due 2017
Debt Instrument [Line Items]
Long-term debt	450		450
Floating-rate notes due 2014
Debt Instrument [Line Items]
Long-term debt	250		250
7.35% notes due 2026
Debt Instrument [Line Items]
Long-term debt	150		150
Extendible notes due 2014
Debt Instrument [Line Items]
Long-term debt	900		1,000
5.25% subordinated notes due 2018
Debt Instrument [Line Items]
Long-term debt	442	[1]	453	[1]
5.30% subordinated notes due 2016
Debt Instrument [Line Items]
Long-term debt	409		414
Floating Rate Subordinated Notes Due2015 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 200		$ 200

[1] We have entered into interest-rate swap agreements, recorded as fair value hedges, to modify our interest expense on these senior and subordinated notes from a fixed rate to a floating rate. As of December 31, 2013, we recorded a decrease of $35 million in the carrying value of long-term debt associated with these fair value hedges. As of December 31, 2012, we recorded an increase of $174 million in the carrying value of long-term debt associated with fair value hedges. Refer to note 16 for additional information about fair value hedges.