Accumulated Other Comprehensive Income - Components of AOCI (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
AOCI [Roll Forward]
Beginning Balance	$ 3,703,829	$ 3,634,977
OCI before reclassifications	70,855	(185,570)
Amounts reclassified from AOCI	10,649	15,500
Net current period OCI	81,504	(170,070)
Ending Balance	3,953,293	3,703,829
Unrealized gains (losses) on available-for-sale securities, net
AOCI [Roll Forward]
Beginning Balance	626,832	796,902
OCI before reclassifications	70,855	(185,570)
Amounts reclassified from AOCI	10,649	15,500
Net current period OCI	81,504	(170,070)
Ending Balance	708,336	626,832
Total Accumulated OCI Balance
AOCI [Roll Forward]
Beginning Balance	626,832	796,902
Ending Balance	$ 708,336	$ 626,832

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount after tax, before reclassification adjustments, of other comprehensive income (loss), attributable to parent.

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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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Amount after tax of reclassification adjustments of other comprehensive income (loss) attributable to parent.

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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