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Recent Accounting Standards - Additional Information (Detail) - USD ($)	Jun. 30, 2020	Jan. 01, 2020	Dec. 31, 2019
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Cumulative-effect adjustment to retained earnings	$ 587,533,000		$ 583,489,000
Minimum \| US Treasury Securities
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Available-for-sale securities maturity range	3 months
Maximum \| US Treasury Securities
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Available-for-sale securities maturity range	1 year
ASU 2016-13 \| Revision Of Prior Period Change In Accounting Principle Adjustment
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Cumulative-effect adjustment to retained earnings		$ 0
ASU 2018-15
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Material capitalized implementation costs	$ 0