Fair Value of Financial Instruments - Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis Quantitative Information about Level 3 Fair Value Measurements (Detail) (USD $) In Millions, unless otherwise specified					6 Months Ended	12 Months Ended	6 Months Ended			12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended			12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended			12 Months Ended	6 Months Ended	12 Months Ended			6 Months Ended	12 Months Ended		6 Months Ended		12 Months Ended	6 Months Ended	12 Months Ended		6 Months Ended		12 Months Ended	6 Months Ended	12 Months Ended		6 Months Ended		12 Months Ended			6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended			6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended			6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended			6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended			6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended			6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2013 Retained Interest in Securitization and Other [Member]	Dec. 31, 2012 Retained Interest in Securitization and Other [Member]	Jun. 30, 2013 Retained Interest in Securitization and Other [Member] Discounted Cash Flows [Member] Constant Prepayment Rate [Member]	Dec. 31, 2012 Retained Interest in Securitization and Other [Member] Discounted Cash Flows [Member] Constant Prepayment Rate [Member]	Jun. 30, 2013 Retained Interest in Securitization and Other [Member] Discounted Cash Flows [Member] Default Rate [Member]	Jun. 30, 2013 Retained Interest in Securitization and Other [Member] Discounted Cash Flows [Member] Loss Severity [Member]	Jun. 30, 2013 Retained Interest in Securitization and Other [Member] Discounted Cash Flows [Member] Discount Rate [Member]	Dec. 31, 2012 Retained Interest in Securitization and Other [Member] Discounted Cash Flows [Member] Discount Rate [Member]	Jun. 30, 2013 Retained Interest in Securitization and Other [Member] Minimum [Member] Discounted Cash Flows [Member]	Dec. 31, 2012 Retained Interest in Securitization and Other [Member] Minimum [Member] Discounted Cash Flows [Member]	Jun. 30, 2013 Retained Interest in Securitization and Other [Member] Minimum [Member] Discounted Cash Flows [Member] Constant Prepayment Rate [Member]	Dec. 31, 2012 Retained Interest in Securitization and Other [Member] Minimum [Member] Discounted Cash Flows [Member] Constant Prepayment Rate [Member]	Jun. 30, 2013 Retained Interest in Securitization and Other [Member] Minimum [Member] Discounted Cash Flows [Member] Default Rate [Member]	Jun. 30, 2013 Retained Interest in Securitization and Other [Member] Minimum [Member] Discounted Cash Flows [Member] Loss Severity [Member]	Jun. 30, 2013 Retained Interest in Securitization and Other [Member] Minimum [Member] Discounted Cash Flows [Member] Discount Rate [Member]	Dec. 31, 2012 Retained Interest in Securitization and Other [Member] Minimum [Member] Discounted Cash Flows [Member] Discount Rate [Member]	Jun. 30, 2013 Retained Interest in Securitization and Other [Member] Maximum [Member] Discounted Cash Flows [Member]	Dec. 31, 2012 Retained Interest in Securitization and Other [Member] Maximum [Member] Discounted Cash Flows [Member]	Jun. 30, 2013 Retained Interest in Securitization and Other [Member] Maximum [Member] Discounted Cash Flows [Member] Constant Prepayment Rate [Member]	Dec. 31, 2012 Retained Interest in Securitization and Other [Member] Maximum [Member] Discounted Cash Flows [Member] Constant Prepayment Rate [Member]	Jun. 30, 2013 Retained Interest in Securitization and Other [Member] Maximum [Member] Discounted Cash Flows [Member] Default Rate [Member]	Jun. 30, 2013 Retained Interest in Securitization and Other [Member] Maximum [Member] Discounted Cash Flows [Member] Loss Severity [Member]	Jun. 30, 2013 Retained Interest in Securitization and Other [Member] Maximum [Member] Discounted Cash Flows [Member] Discount Rate [Member]	Dec. 31, 2012 Retained Interest in Securitization and Other [Member] Maximum [Member] Discounted Cash Flows [Member] Discount Rate [Member]	Jun. 30, 2013 Retained Interest in Securitization and Other [Member] Average [Member] Discounted Cash Flows [Member]	Dec. 31, 2012 Retained Interest in Securitization and Other [Member] Average [Member] Discounted Cash Flows [Member]	Jun. 30, 2013 Mortgage Servicing Rights [Member]	Dec. 31, 2012 Mortgage Servicing Rights [Member]	Jun. 30, 2013 Mortgage Servicing Rights [Member] Servicing Cost ($ Per Loan) [Member]	Dec. 31, 2013 Mortgage Servicing Rights [Member] Servicing Cost ($ Per Loan) [Member]	Dec. 31, 2012 Mortgage Servicing Rights [Member] Discounted Cash Flows [Member] Constant Prepayment Rate [Member]	Jun. 30, 2013 Mortgage Servicing Rights [Member] Discounted Cash Flows [Member] Total Prepayment Rate [Member]	Jun. 30, 2013 Mortgage Servicing Rights [Member] Discounted Cash Flows [Member] Discount Rate [Member]	Dec. 31, 2012 Mortgage Servicing Rights [Member] Discounted Cash Flows [Member] Discount Rate [Member]	Jun. 30, 2013 Mortgage Servicing Rights [Member] Minimum [Member] Servicing Cost ($ Per Loan) [Member]	Dec. 31, 2013 Mortgage Servicing Rights [Member] Minimum [Member] Servicing Cost ($ Per Loan) [Member]	Dec. 31, 2012 Mortgage Servicing Rights [Member] Minimum [Member] Discounted Cash Flows [Member] Constant Prepayment Rate [Member]	Jun. 30, 2013 Mortgage Servicing Rights [Member] Minimum [Member] Discounted Cash Flows [Member] Total Prepayment Rate [Member]	Jun. 30, 2013 Mortgage Servicing Rights [Member] Minimum [Member] Discounted Cash Flows [Member] Discount Rate [Member]	Dec. 31, 2012 Mortgage Servicing Rights [Member] Minimum [Member] Discounted Cash Flows [Member] Discount Rate [Member]	Jun. 30, 2013 Mortgage Servicing Rights [Member] Maximum [Member] Servicing Cost ($ Per Loan) [Member]	Dec. 31, 2013 Mortgage Servicing Rights [Member] Maximum [Member] Servicing Cost ($ Per Loan) [Member]	Dec. 31, 2012 Mortgage Servicing Rights [Member] Maximum [Member] Discounted Cash Flows [Member] Constant Prepayment Rate [Member]	Jun. 30, 2013 Mortgage Servicing Rights [Member] Maximum [Member] Discounted Cash Flows [Member] Total Prepayment Rate [Member]	Jun. 30, 2013 Mortgage Servicing Rights [Member] Maximum [Member] Discounted Cash Flows [Member] Discount Rate [Member]	Dec. 31, 2012 Mortgage Servicing Rights [Member] Maximum [Member] Discounted Cash Flows [Member] Discount Rate [Member]	Jun. 30, 2013 Residential Mortgage-Backed Securities [Member]	Dec. 31, 2012 Residential Mortgage-Backed Securities [Member]	Jun. 30, 2013 Residential Mortgage-Backed Securities [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Yield [Member]	Dec. 31, 2012 Residential Mortgage-Backed Securities [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Yield [Member]	Jun. 30, 2013 Residential Mortgage-Backed Securities [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Constant Prepayment Rate [Member]	Dec. 31, 2012 Residential Mortgage-Backed Securities [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Constant Prepayment Rate [Member]	Jun. 30, 2013 Residential Mortgage-Backed Securities [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Default Rate [Member]	Dec. 31, 2012 Residential Mortgage-Backed Securities [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Default Rate [Member]	Jun. 30, 2013 Residential Mortgage-Backed Securities [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Loss Severity [Member]	Dec. 31, 2012 Residential Mortgage-Backed Securities [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Loss Severity [Member]	Jun. 30, 2013 Residential Mortgage-Backed Securities [Member] Minimum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Yield [Member]	Dec. 31, 2012 Residential Mortgage-Backed Securities [Member] Minimum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Yield [Member]	Jun. 30, 2013 Residential Mortgage-Backed Securities [Member] Minimum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Constant Prepayment Rate [Member]	Dec. 31, 2012 Residential Mortgage-Backed Securities [Member] Minimum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Constant Prepayment Rate [Member]	Jun. 30, 2013 Residential Mortgage-Backed Securities [Member] Minimum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Default Rate [Member]	Dec. 31, 2012 Residential Mortgage-Backed Securities [Member] Minimum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Default Rate [Member]	Jun. 30, 2013 Residential Mortgage-Backed Securities [Member] Minimum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Loss Severity [Member]	Dec. 31, 2012 Residential Mortgage-Backed Securities [Member] Minimum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Loss Severity [Member]	Jun. 30, 2013 Residential Mortgage-Backed Securities [Member] Maximum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Yield [Member]	Dec. 31, 2012 Residential Mortgage-Backed Securities [Member] Maximum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Yield [Member]	Jun. 30, 2013 Residential Mortgage-Backed Securities [Member] Maximum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Constant Prepayment Rate [Member]	Dec. 31, 2012 Residential Mortgage-Backed Securities [Member] Maximum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Constant Prepayment Rate [Member]	Jun. 30, 2013 Residential Mortgage-Backed Securities [Member] Maximum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Default Rate [Member]	Dec. 31, 2012 Residential Mortgage-Backed Securities [Member] Maximum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Default Rate [Member]	Jun. 30, 2013 Residential Mortgage-Backed Securities [Member] Maximum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Loss Severity [Member]	Dec. 31, 2012 Residential Mortgage-Backed Securities [Member] Maximum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Loss Severity [Member]	Jun. 30, 2013 Commercial Mortgage-Backed Securities [Member]	Dec. 31, 2012 Commercial Mortgage-Backed Securities [Member]	Jun. 30, 2013 Commercial Mortgage-Backed Securities [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Yield [Member]	Dec. 31, 2012 Commercial Mortgage-Backed Securities [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Yield [Member]	Jun. 30, 2013 Commercial Mortgage-Backed Securities [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Constant Prepayment Rate [Member]	Dec. 31, 2012 Commercial Mortgage-Backed Securities [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Constant Prepayment Rate [Member]	Jun. 30, 2013 Commercial Mortgage-Backed Securities [Member] Minimum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Yield [Member]	Dec. 31, 2012 Commercial Mortgage-Backed Securities [Member] Minimum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Yield [Member]	Jun. 30, 2013 Commercial Mortgage-Backed Securities [Member] Minimum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Constant Prepayment Rate [Member]	Dec. 31, 2012 Commercial Mortgage-Backed Securities [Member] Minimum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Constant Prepayment Rate [Member]	Jun. 30, 2013 Commercial Mortgage-Backed Securities [Member] Maximum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Yield [Member]	Dec. 31, 2012 Commercial Mortgage-Backed Securities [Member] Maximum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Yield [Member]	Jun. 30, 2013 Commercial Mortgage-Backed Securities [Member] Maximum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Constant Prepayment Rate [Member]	Dec. 31, 2012 Commercial Mortgage-Backed Securities [Member] Maximum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Constant Prepayment Rate [Member]	Jun. 30, 2013 Other Asset-Backed Securities [Member]	Dec. 31, 2012 Other Asset-Backed Securities [Member]	Jun. 30, 2013 Other Asset-Backed Securities [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Yield [Member]	Dec. 31, 2012 Other Asset-Backed Securities [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Yield [Member]	Jun. 30, 2013 Other Asset-Backed Securities [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Constant Prepayment Rate [Member]	Dec. 31, 2012 Other Asset-Backed Securities [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Constant Prepayment Rate [Member]	Jun. 30, 2013 Other Asset-Backed Securities [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Default Rate [Member]	Dec. 31, 2012 Other Asset-Backed Securities [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Default Rate [Member]	Jun. 30, 2013 Other Asset-Backed Securities [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Loss Severity [Member]	Dec. 31, 2012 Other Asset-Backed Securities [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Loss Severity [Member]	Jun. 30, 2013 Other Asset-Backed Securities [Member] Minimum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Yield [Member]	Dec. 31, 2012 Other Asset-Backed Securities [Member] Minimum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Yield [Member]	Jun. 30, 2013 Other Asset-Backed Securities [Member] Minimum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Constant Prepayment Rate [Member]	Dec. 31, 2012 Other Asset-Backed Securities [Member] Minimum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Constant Prepayment Rate [Member]	Jun. 30, 2013 Other Asset-Backed Securities [Member] Minimum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Default Rate [Member]	Dec. 31, 2012 Other Asset-Backed Securities [Member] Minimum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Default Rate [Member]	Jun. 30, 2013 Other Asset-Backed Securities [Member] Minimum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Loss Severity [Member]	Dec. 31, 2012 Other Asset-Backed Securities [Member] Minimum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Loss Severity [Member]	Jun. 30, 2013 Other Asset-Backed Securities [Member] Maximum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Yield [Member]	Dec. 31, 2012 Other Asset-Backed Securities [Member] Maximum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Yield [Member]	Jun. 30, 2013 Other Asset-Backed Securities [Member] Maximum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Constant Prepayment Rate [Member]	Dec. 31, 2012 Other Asset-Backed Securities [Member] Maximum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Constant Prepayment Rate [Member]	Jun. 30, 2013 Other Asset-Backed Securities [Member] Maximum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Default Rate [Member]	Dec. 31, 2012 Other Asset-Backed Securities [Member] Maximum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Default Rate [Member]	Jun. 30, 2013 Other Asset-Backed Securities [Member] Maximum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Loss Severity [Member]	Dec. 31, 2012 Other Asset-Backed Securities [Member] Maximum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Loss Severity [Member]	Jun. 30, 2013 U.S. Government Guaranteed Debt and Other [Member]	Dec. 31, 2012 U.S. Government Guaranteed Debt and Other [Member]	Jun. 30, 2013 U.S. Government Guaranteed Debt and Other [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Yield [Member]	Dec. 31, 2012 U.S. Government Guaranteed Debt and Other [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Yield [Member]	Jun. 30, 2013 U.S. Government Guaranteed Debt and Other [Member] Minimum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Yield [Member]	Dec. 31, 2012 U.S. Government Guaranteed Debt and Other [Member] Minimum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Yield [Member]	Jun. 30, 2013 U.S. Government Guaranteed Debt and Other [Member] Maximum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Yield [Member]	Dec. 31, 2012 U.S. Government Guaranteed Debt and Other [Member] Maximum [Member] Discounted Cash Flows (3rd Party Pricing) [Member] Yield [Member]	Jun. 30, 2013 Derivative Assets [Member]	Dec. 31, 2012 Derivative Assets [Member]	Jun. 30, 2013 Derivative Assets [Member] Discounted Cash Flows [Member] Swap Rates [Member]	Dec. 31, 2012 Derivative Assets [Member] Discounted Cash Flows [Member] Swap Rates [Member]	Jun. 30, 2013 Derivative Assets [Member] Minimum [Member] Discounted Cash Flows [Member] Swap Rates [Member]	Dec. 31, 2012 Derivative Assets [Member] Minimum [Member] Discounted Cash Flows [Member] Swap Rates [Member]	Jun. 30, 2013 Derivative Assets [Member] Maximum [Member] Discounted Cash Flows [Member] Swap Rates [Member]	Dec. 31, 2012 Derivative Assets [Member] Maximum [Member] Discounted Cash Flows [Member] Swap Rates [Member]	Jun. 30, 2013 Derivative Liabilities [Member]	Dec. 31, 2012 Derivative Liabilities [Member]	Jun. 30, 2013 Derivative Liabilities [Member] Discounted Cash Flows [Member] Swap Rates [Member]	Dec. 31, 2012 Derivative Liabilities [Member] Discounted Cash Flows [Member] Swap Rates [Member]	Jun. 30, 2013 Derivative Liabilities [Member] Minimum [Member] Discounted Cash Flows [Member] Swap Rates [Member]	Dec. 31, 2012 Derivative Liabilities [Member] Minimum [Member] Discounted Cash Flows [Member] Swap Rates [Member]	Jun. 30, 2013 Derivative Liabilities [Member] Maximum [Member] Discounted Cash Flows [Member] Swap Rates [Member]	Dec. 31, 2012 Derivative Liabilities [Member] Maximum [Member] Discounted Cash Flows [Member] Swap Rates [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Assets	$ 64,031	$ 66,086	$ 198	$ 204																									$ 61	$ 55																			$ 1,535	$ 1,335																									$ 461	$ 587													$ 109	$ 102																									$ 848	$ 665							$ 72	$ 90
Fair Value, Liabilities																																																																																																																																			$ 42	$ 38
Range													1.40%	1.25%	1.39%	16.91%	4.18%	2.90%			15.00%	22.21%	8.39%	89.22%	13.57%	13.57%													11.77%	11.12%	9.95%	9.95%			32.99%	32.43%	17.07%	37.88%											0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	4.00%	25.00%	24.00%	24.00%	26.00%	20.00%	21.00%	75.00%	75.00%							2.00%	1.00%	0.00%	0.00%	4.00%	3.00%	15.00%	15.00%											3.00%	1.00%	0.00%	0.00%	2.00%	1.00%	45.00%	46.00%	9.00%	24.00%	6.00%	5.00%	28.00%	28.00%	88.00%	88.00%					0.00%	1.00%	4.00%	4.00%					2.69%	1.82%	3.31%	2.58%					2.71%	1.82%	3.29%	2.55%
Weighted Average					6.67%	13.52%	5.64%	25.77%	13.20%	12.70%																							19.37%	18.09%	11.17%	12.66%															6.00%	5.00%	5.00%	6.00%	8.00%	9.00%	50.00%	52.00%																			3.00%	2.00%	3.00%	11.00%											5.00%	4.00%	2.00%	2.00%	13.00%	15.00%	71.00%	72.00%																			2.00%	2.00%							3.23%	2.46%							3.21%	2.42%
Servicing cost																															91	302					82	81					408	864
Life of receivables (months)											35 months	29 months							87 months	243 months							71 months	66 months