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Fair Value Measurements - Summary of Changes in Level 3 Fair Value Category (Detail) (USD $) In Thousands, unless otherwise specified | 12 Months Ended
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Dec. 31, 2012 | Dec. 31, 2011
Level 3 [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |
Balance, beginning of period | $ 14,019,216 | $ 15,874,572
Additions of VIEs consolidated |  | (350,624)
Included in earnings | 721,347 | 513,876
Included in other comprehensive income | 650,373 | (20,630)
Purchases |  |
Issuances | (162,460) |
Sales |  | (16,600)
Settlements | (439,649) | (355,313)
Transfers in Level 3 | (1,816,216) | (905,195)
Transfers out of Level 3 | 1,443,877 | 880,154
Deconsolidation of VIEs |  | (1,601,024)
Balance, end of period | 14,416,488 | 14,019,216
The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date | 587,983 | 512,287
Investments contract [Member] | Level 3 [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |
Balance, beginning of period | 2,199,338 | 1,904,361
Included in earnings | (41,289) | 311,842
Included in other comprehensive income | 103,245 | (16,865)
Purchases |  |
Balance, end of period | 2,261,294 | 2,199,338
The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date | (41,289) | 311,842
Loans [Member] | Level 3 [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |
Balance, beginning of period | 14,126,994 | 15,800,918
Included in earnings | 952,463 | 664,823
Included in other comprehensive income | 637,954 | (14,881)
Purchases |  |
Settlements | (358,338) | (428,899)
Deconsolidation of VIEs |  | (1,894,967)
Balance, end of period | 15,359,073 | 14,126,994
The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date | 952,944 | 664,823
Derivatives liabilities [Member] | Level 3 [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |
Balance, beginning of period |  | 4,511
Included in earnings |  | (4,511)
Purchases |  |
The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date |  | (4,511)
Long-term debt [Member] | Level 3 [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |
Balance, beginning of period | (1,934,642) | (1,856,366)
Additions of VIEs consolidated |  | (350,624)
Included in earnings | (208,678) | (118,048)
Included in other comprehensive income | (98,311) | 11,240
Purchases |  |
Issuances | (162,460) |
Settlements | 64,781 | 35,241
Transfers in Level 3 | (1,875,121) | (905,664)
Transfers out of Level 3 | 1,257,930 | 955,636
Deconsolidation of VIEs |  | 293,943
Balance, end of period | (2,956,501) | (1,934,642)
The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date | (208,678) | (118,063)
Investment by class [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |
Balance, beginning of period | 97,522 | 199,172
Included in earnings | (3) | (3,467)
Included in other comprehensive income | 7,485 | (124)
Purchases |  |
Sales |  | (16,600)
Settlements | (97,206) | (6,446)
Transfers in Level 3 | 58,905 | 469
Transfers out of Level 3 | (6,301) | (75,482)
Balance, end of period | 60,402 | 97,522
Investment by class [Member] | Other Asset Backed Securities [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |
Balance, beginning of period | 75,886 | 159,473
Included in other comprehensive income | 7,051 | (6,612)
Purchases |  |
Settlements | (85,741) | (1,493)
Transfers in Level 3 | 53,068 |
Transfers out of Level 3 |  | (75,482)
Balance, end of period | 50,264 | 75,886
Investment by class [Member] | U.S. Agency Obligations [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |
Balance, beginning of period | 1,224 | 1,197
Included in earnings | (2) | (4)
Included in other comprehensive income | (9) | (4)
Purchases |  |
Settlements | (749) | (434)
Transfers in Level 3 |  | 469
Transfers out of Level 3 | (464) |
Balance, end of period |  | 1,224
Derivatives by class [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |
Balance, beginning of period | (486,775) | (195,933)
Included in earnings | 21,076 | (335,633)
Purchases |  |
Settlements | (48,886) | 44,791
Transfers out of Level 3 | 192,248 |
Balance, end of period | (322,337) | (486,775)
The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date | (113,836) | (340,674)
Investments [Member] | Level 3 [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |
Balance, beginning of period | 97,522 | 199,172
Included in earnings | (3) | (3,467)
Included in other comprehensive income | 7,485 | (124)
Purchases |  |
Sales |  | (16,600)
Settlements | (97,206) | (6,446)
Transfers in Level 3 | 58,905 | 469
Transfers out of Level 3 | (6,301) | (75,482)
Balance, end of period | 60,402 | 97,522
Other Assets [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |
Included in earnings | (2,222) | (1,130)
Other Assets [Member] | Level 3 [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |
Balance, beginning of period | 16,779 | 17,909
Included in earnings | (2,222) | (1,130)
Purchases |  |
Balance, end of period | 14,557 | 16,779
The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date | (2,222) | (1,130)
Derivatives assets [Member] | Level 3 [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |
Balance, beginning of period | (486,775) | (195,933)
Included in earnings | 21,076 | (335,633)
Purchases |  |
Settlements | (48,886) | 44,791
Transfers out of Level 3 | 192,248 |
Balance, end of period | (322,337) | (486,775)
The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date | (113,836) | (340,674)
Collateralized debt obligations [Member] | Investment by class [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |
Balance, beginning of period | 12,482 | 30,433
Included in earnings | (5) | (3,286)
Included in other comprehensive income | 646 | 6,454
Purchases |  |
Sales |  | (16,600)
Settlements | (6,641) | (4,519)
Balance, end of period | 6,482 | 12,482
Corporate obligations [Member] | Investment by class [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |
Balance, beginning of period | 7,930 | 8,069
Included in earnings | 4 | (177)
Included in other comprehensive income | (203) | 38
Purchases |  |
Settlements | (4,075) |
Transfers in Level 3 | 5,837 |
Transfers out of Level 3 | (5,837) |
Balance, end of period | 3,656 | 7,930
Interest rate swaps [Member] | Derivatives by class [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |
Balance, beginning of period | (302,177) | 25,751
Included in earnings | (70,415) | (389,720)
Purchases |  |
Settlements | 71,592 | 61,792
Transfers out of Level 3 | 192,248 |
Balance, end of period | (108,752) | (302,177)
The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date | (78,505) | (356,354)
Credit Derivatives [Member] | Derivatives by class [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |
Balance, beginning of period | (190,653) | (221,684)
Included in earnings | (9,219) | 48,032
Purchases |  |
Settlements | (13,713) | (17,001)
Balance, end of period | (213,585) | (190,653)
The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date | (35,331) | 9,625
Call options on long-term debt [Member] | Derivatives by class [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items] |  |
Balance, beginning of period | 6,055 |
Included in earnings | 100,710 | 6,055
Purchases |  |
Settlements | (106,765) |
Balance, end of period |  | 6,055
The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date |  | $ 6,055

X
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