Fair Value Measurements - Information about Valuation Inputs for Fixed Income Securities Classified as Level 3 (Detail) - USD ($)
$ in Thousands

3 Months Ended

6 Months Ended

Jun. 30, 2019

Jun. 30, 2018

Jun. 30, 2019

Jun. 30, 2018

Mar. 31, 2019

Dec. 31, 2018

Mar. 31, 2018

Dec. 31, 2017

Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability

$ 74,318

$ 68,802

$ 74,318

$ 68,802

$ 72,071

$ 808,557

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings

771

35,466

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss

2,114

(56,022)

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Issues

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements

(638)

(713,890)

Variable Interest Entity, Primary Beneficiary [Member]

Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)

Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held

334,834

(71,072)

Fair Value, Inputs, Level 3 [Member]

Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability

7,080,205

11,110,155

7,080,205

11,110,155

$ 7,138,755

6,930,446

$ 11,950,737

12,561,185

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings

193,064

37,791

353,413

(48,387)

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss

(162,585)

(691,566)

(27,898)

(313,415)

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Issues

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Sales

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements

(89,029)

(181,498)

(175,756)

(1,083,919)

Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held

192,580

37,418

352,455

(84,050)

Fair Value, Inputs, Level 3 [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Corporate Obligations [Member]

Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability

2,914,145

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings

(73,163)

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss

(66,463)

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Issues

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Sales

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements

(17,595)

Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held

(73,163)

Derivative [Member]

Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability

62,270

45,613

62,270

45,613

53,034

46,001

49,908

60,808

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings

10,366

(2,682)

18,553

(12,057)

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Issues

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Sales

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements

(1,130)

(1,613)

(2,284)

3,138

Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held

10,270

(2,773)

18,366

(12,254)

Interest Rate Swap [Member]

Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability

63,131

47,460

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings

17,770

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Issues

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Sales

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements

(2,099)

Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held

17,770

Credit Derivative [Member]

Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability

(861)

$ (1,459)

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings

783

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Issues

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Sales

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements

(185)

Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held

596

Credit Derivative [Member] | Derivative [Member]

Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability

(1,326)

(566)

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings

(563)

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Issues

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Sales

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements

197

Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held

(760)

Credit Derivative [Member] | Credit Derivative [Member]

Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability

(861)

(1,326)

(861)

(1,326)

(1,077)

(1,018)

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings

310

(217)

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Issues

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Sales

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements

(94)

(91)

Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held

214

(308)

Interest Rate Swap [Member] | Derivative [Member]

Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability

46,939

$ 61,374

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings

(11,494)

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Issues

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Sales

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements

(2,941)

Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held

(11,494)

Interest Rate Swap [Member] | Interest Rate Swap [Member]

Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability

63,131

46,939

$ 63,131

$ 46,939

$ 54,111

$ 50,926

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings

10,056

(2,465)

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Issues

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Sales

Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements

(1,036)

(1,522)

Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held

$ 10,056

$ (2,465)