Current Expected Credit Losses (CECL) - Schedule of Portfolio Segment by Class of Financing Receivables, Credit Quality Indicator and Origination Year (Detail) - Class of Financing Receivables, Credit Quality Indicator and Origination [Member] $ in Thousands	Mar. 31, 2020 USD ($)
Accrued Commissions Receivable [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, amortized cost basis, total	$ 421,894
Financing receivable, amortized cost basis by origination year, 2020	272,074
Financing receivable, amortized cost basis by origination year, 2019	113,379
Financing receivable, amortized cost basis by origination year, 2018	25,399
Financing receivable, amortized cost basis by origination year, 2017	6,878
Financing receivable, amortized cost basis by origination year, Prior	4,164
Employee-Related Receivables [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, amortized cost basis, total	6,222
Financing receivable, amortized cost basis by origination year, 2020	605
Financing receivable, amortized cost basis by origination year, 2019	3,323
Financing receivable, amortized cost basis by origination year, 2018	1,052
Financing receivable, amortized cost basis by origination year, 2017	375
Financing receivable, amortized cost basis by origination year, Prior	867
Less Than 1 Year [Member] | Accrued Commissions Receivable [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, amortized cost basis, total	371,270
Financing receivable, amortized cost basis by origination year, 2020	272,074
Financing receivable, amortized cost basis by origination year, 2019	99,196
Less Than 1 Year [Member] | Employee-Related Receivables [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, amortized cost basis, total	3,009
Financing receivable, amortized cost basis by origination year, 2020	605
Financing receivable, amortized cost basis by origination year, 2019	2,404
1 Year - Less Than 2 Years [Member] | Accrued Commissions Receivable [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, amortized cost basis, total	34,468
Financing receivable, amortized cost basis by origination year, 2019	14,183
Financing receivable, amortized cost basis by origination year, 2018	20,285
1 Year - Less Than 2 Years [Member] | Employee-Related Receivables [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, amortized cost basis, total	1,888
Financing receivable, amortized cost basis by origination year, 2019	919
Financing receivable, amortized cost basis by origination year, 2018	969
2 Years and Greater [Member] | Accrued Commissions Receivable [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, amortized cost basis, total	16,156
Financing receivable, amortized cost basis by origination year, 2018	5,114
Financing receivable, amortized cost basis by origination year, 2017	6,878
Financing receivable, amortized cost basis by origination year, Prior	4,164
2 Years and Greater [Member] | Employee-Related Receivables [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Financing receivable, amortized cost basis, total	1,325
Financing receivable, amortized cost basis by origination year, 2018	83
Financing receivable, amortized cost basis by origination year, 2017	375
Financing receivable, amortized cost basis by origination year, Prior	$ 867