Investments - Carrying Value and Amortized Cost of Company's Investments Summarized by Major Security Type (Parenthetical) (Detail) $ in Thousands	12 Months Ended
Dec. 31, 2020 USD ($)
Corporate debt securities \| Maximum
Schedule of Available-for-sale Securities [Line Items]
Unrealized loss on securities	$ 500

The increase (decrease), resulting in a loss, in the difference between the fair value and the carrying value, or in the comparative fair values, of securities held at each balance sheet date, that was included in earnings for the period.

No definition available.

Name:	us-gaap_UnrealizedLossOnSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration