Borrowings and Contractual Commitments Long-term debt (Details) (USD $) In Millions, unless otherwise specified							12 Months Ended														12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2012 Subsidiaries [Member]	Dec. 31, 2011 Subsidiaries [Member]	Dec. 31, 2012 Subsidiaries [Member] Fixed Interest Rate Debt [Member] Subordinated Debt [Member]	Dec. 31, 2012 Subsidiaries [Member] Fixed Interest Rate Debt [Member] Senior Notes [Member]	Dec. 31, 2012 Subsidiaries [Member] Variable Rate Debt [Member] Subordinated Debt [Member]	Dec. 31, 2012 Subsidiaries [Member] Variable Rate Debt [Member] Senior Notes [Member]	Dec. 31, 2012 Subsidiaries [Member] Senior Notes [Member]		Dec. 31, 2011 Subsidiaries [Member] Senior Notes [Member]		Dec. 31, 2012 Subsidiaries [Member] Subordinated Debt [Member]		Dec. 31, 2011 Subsidiaries [Member] Subordinated Debt [Member]		Dec. 31, 2012 Parent Company [Member]	Dec. 31, 2011 Parent Company [Member]	Dec. 31, 2012 Parent Company [Member] Fixed Interest Rate Debt [Member] Subordinated Debt [Member]	Dec. 31, 2011 Parent Company [Member] Fixed Interest Rate Debt [Member] Junior Subordinated Debt [Member]	Dec. 31, 2012 Parent Company [Member] Fixed Interest Rate Debt [Member] Senior Notes [Member]	Dec. 31, 2012 Parent Company [Member] Variable Rate Debt [Member] Junior Subordinated Debt [Member]	Dec. 31, 2012 Parent Company [Member] Variable Rate Debt [Member] Senior Notes [Member]	Dec. 31, 2012 Parent Company [Member] Junior Subordinated Debt [Member]	Dec. 31, 2011 Parent Company [Member] Junior Subordinated Debt [Member]	Dec. 31, 2012 Parent Company [Member] Senior Notes [Member]	Dec. 31, 2011 Parent Company [Member] Senior Notes [Member]		Dec. 31, 2012 Parent Company [Member] Subordinated Debt [Member]	Dec. 31, 2011 Parent Company [Member] Subordinated Debt [Member]	Dec. 31, 2012 Lower Limit Subsidiaries [Member] Subordinated Debt [Member]	Dec. 31, 2012 Lower Limit Subsidiaries [Member] Senior Notes [Member]	Dec. 31, 2012 Lower Limit Parent Company [Member] Junior Subordinated Debt [Member]	Dec. 31, 2011 Lower Limit Parent Company [Member] Junior Subordinated Debt [Member]	Dec. 31, 2012 Lower Limit Parent Company [Member] Senior Notes [Member]	Dec. 31, 2012 Upper Limit Subsidiaries [Member] Subordinated Debt [Member]	Dec. 31, 2012 Upper Limit Subsidiaries [Member] Senior Notes [Member]	Dec. 31, 2012 Upper Limit Parent Company [Member] Junior Subordinated Debt [Member]	Dec. 31, 2011 Upper Limit Parent Company [Member] Junior Subordinated Debt [Member]	Dec. 31, 2012 Upper Limit Parent Company [Member] Senior Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Fixed Interest, Amount											$ 426	[1]	$ 350	[1]												$ 0	$ 1,197	$ 2,270	$ 2,719	[2]	$ 200	$ 200
Long-term Debt, Percentage Bearing Variable Interest, Amount											3,846	[3]	2,504	[3]	500		500									627	651	152	1,527
Debt Instrument, Fair Value Disclosure															1,336	[4]	1,260	[4]
Long-term Debt	$ 9,357	[5]	$ 10,908	[5]	$ 6,108	$ 4,614													$ 3,249	$ 6,294
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate																																	0.60%	0.41%	0.96%		0.46%	0.66%	7.50%	1.34%		4.00%
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate																															6.00%		5.00%	0.50%		6.10%	1.00%	7.25%	9.65%		7.88%	6.00%
Debt Instrument, Maturity Date																					Feb. 15, 2026
Debt Instrument, Maturity Date Range, Start							Sep. 01, 2015	Mar. 11, 2013	Apr. 01, 2015	Jun. 27, 2013												Dec. 15, 2036	Jul. 29, 2014	Apr. 01, 2027	Oct. 31, 2013
Debt Instrument, Maturity Date Range, End							Apr. 01, 2020	Jul. 31, 2048	Aug. 24, 2015	Oct. 01, 2037												Mar. 15, 2068	Jan. 15, 2028	Mar. 15, 2028	Aug. 01, 2019

[1] Includes leases and other obligations that do not have a stated interest rate.

[2] Includes $0 and $448 million of debt recorded at fair value at December 31, 2012 and 2011, respectively.

[3] Includes $286 million and $289 million of debt recorded at fair value at December 31, 2012 and 2011, respectively.

[4] Debt recorded at fair value.

[5] 3 Includes debt of consolidated VIEs ($286 and $289 at fair value as of December 31, 2012 and December 31, 2011, respectively)666 722