Summary of Significant Accounting Policies - Schedule of Gross Carrying Values, Accumulated Amortization and Net Carrying Amounts of Major Classes of Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Finite Lived Intangible Assets [Line Items]
Gross	$ 39,900	$ 39,900
Accumulated amortization, intangible assets	10,939	6,952
Net	28,961	32,948
Customer Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Gross	39,500	39,500
Accumulated amortization, intangible assets	10,679	6,729
Net	28,821	32,771
Tradenames [Member]
Finite Lived Intangible Assets [Line Items]
Gross	200	200
Accumulated amortization, intangible assets	200	183
Net		17
Leasehold Interests [Member]
Finite Lived Intangible Assets [Line Items]
Gross	200	200
Accumulated amortization, intangible assets	60	40
Net	$ 140	$ 160