Commitments and Contingencies - Fair Value of Annuities (Detail) $ in Thousands	Dec. 31, 2020 USD ($)
Commitments And Contingencies [Line Items]
Statement value of annuities exceeding 1% of statutory surplus	$ 99,275
Pacific Life and Annuity Company [Member] | A.M. Best Rating, A+ [Member]
Commitments And Contingencies [Line Items]
Statement value of annuities exceeding 1% of statutory surplus	16,489
American General Life Insurance Company [Member] | A.M. Best Rating, A [Member]
Commitments And Contingencies [Line Items]
Statement value of annuities exceeding 1% of statutory surplus	14,462
New York Life Insurance Company [Member] | A.M. Best Rating, A++ [Member]
Commitments And Contingencies [Line Items]
Statement value of annuities exceeding 1% of statutory surplus	9,120
Travelers Life and Annuity Insurance Company [Member] | A.M. Best Rating, A [Member]
Commitments And Contingencies [Line Items]
Statement value of annuities exceeding 1% of statutory surplus	9,758
Metropolitan Life Insurance Company [Member] | A.M. Best Rating, A+ [Member]
Commitments And Contingencies [Line Items]
Statement value of annuities exceeding 1% of statutory surplus	6,701
John Hancock Life Insurance Company [Member] | A.M. Best Rating, A+ [Member]
Commitments And Contingencies [Line Items]
Statement value of annuities exceeding 1% of statutory surplus	6,536
Athene Annuity and Life Company [Member] | A.M. Best Rating, A [Member]
Commitments And Contingencies [Line Items]
Statement value of annuities exceeding 1% of statutory surplus	4,363
United of Omaha Life Insurance Company [Member] | A.M. Best Rating, A+ [Member]
Commitments And Contingencies [Line Items]
Statement value of annuities exceeding 1% of statutory surplus	5,141
Lincoln Life Assurance Company of Boston [Member] | A.M. Best Rating, A [Member]
Commitments And Contingencies [Line Items]
Statement value of annuities exceeding 1% of statutory surplus	3,698
Pacific Life Insurance Company [Member] | A.M. Best Rating, A+ [Member]
Commitments And Contingencies [Line Items]
Statement value of annuities exceeding 1% of statutory surplus	4,010
Other [Member]
Commitments And Contingencies [Line Items]
Statement value of annuities exceeding 1% of statutory surplus	$ 18,997