Schedule of Outstanding Debt (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2021
Secured Equipment Notes due in 2026 [Member]
Debt Instrument [Line Items]
Equipment notes due period	2026
Payment Frequency	monthly
Secured Equipment Notes due in 2026 [Member] | Commencing on 2021 [Member]
Debt Instrument [Line Items]
Equipment notes, date of first required payment	2021
Secured Equipment Notes due in 2025 [Member]
Debt Instrument [Line Items]
Equipment notes due period	2025
Payment Frequency	monthly
Secured Equipment Notes due in 2025 [Member] | Commencing on 2021 [Member]
Debt Instrument [Line Items]
Equipment notes, date of first required payment	2021
Secured Equipment Notes due in 2025 [Member] | Commencing on 2020 [Member]
Debt Instrument [Line Items]
Equipment notes, date of first required payment	2020
Secured Equipment Notes due in 2024 [Member]
Debt Instrument [Line Items]
Equipment notes due period	2024
Payment Frequency	monthly
Secured Equipment Notes due in 2024 [Member] | Commencing on 2020 [Member]
Debt Instrument [Line Items]
Equipment notes, date of first required payment	2020
Secured Equipment Notes due in 2024 [Member] | Commencing on 2019 [Member]
Debt Instrument [Line Items]
Equipment notes, date of first required payment	2019
Secured Equipment Notes due in 2024 [Member] | Commencing on 2017 [Member]
Debt Instrument [Line Items]
Equipment notes, date of first required payment	2017
Secured Equipment Notes due in 2021 [Member]
Debt Instrument [Line Items]
Equipment notes due period	2021
Payment Frequency	monthly
Secured Equipment Notes due in 2021 [Member] | Commencing on 2014 [Member]
Debt Instrument [Line Items]
Equipment notes, date of first required payment	2014
Secured Equipment Notes due in 2021 [Member] | Commencing on 2016 [Member]
Debt Instrument [Line Items]
Equipment notes, date of first required payment	2016
Secured Equipment Notes due in 2023 [Member]
Debt Instrument [Line Items]
Equipment notes due period	2023
Payment Frequency	monthly
Secured Equipment Notes due in 2023 [Member] | Commencing on 2019 [Member]
Debt Instrument [Line Items]
Equipment notes, date of first required payment	2019
Secured Equipment Notes due in 2023 [Member] | Commencing on 2016 [Member]
Debt Instrument [Line Items]
Equipment notes, date of first required payment	2016
Secured Equipment Notes due in 2022 [Member]
Debt Instrument [Line Items]
Equipment notes due period	2022
Payment Frequency	monthly
Secured Equipment Notes due in 2022 [Member] | Commencing on 2017 [Member]
Debt Instrument [Line Items]
Equipment notes, date of first required payment	2017
Secured Equipment Notes due in 2022 [Member] | Commencing on 2015 [Member]
Debt Instrument [Line Items]
Equipment notes, date of first required payment	2015
Minimum [Member] | Secured Equipment Notes due in 2026 [Member]
Debt Instrument [Line Items]
Interest rate secured debt	1.48%
Minimum [Member] | Secured Equipment Notes due in 2025 [Member]
Debt Instrument [Line Items]
Interest rate secured debt	1.51%
Minimum [Member] | Secured Equipment Notes due in 2024 [Member]
Debt Instrument [Line Items]
Interest rate secured debt	2.50%
Minimum [Member] | Secured Equipment Notes due in 2021 [Member]
Debt Instrument [Line Items]
Interest rate secured debt	2.02%
Minimum [Member] | Secured Equipment Notes due in 2023 [Member]
Debt Instrument [Line Items]
Interest rate secured debt	2.20%
Minimum [Member] | Secured Equipment Notes due in 2022 [Member]
Debt Instrument [Line Items]
Interest rate secured debt	2.20%
Maximum [Member] | Secured Equipment Notes due in 2026 [Member]
Debt Instrument [Line Items]
Interest rate secured debt	2.41%
Maximum [Member] | Secured Equipment Notes due in 2025 [Member]
Debt Instrument [Line Items]
Interest rate secured debt	1.80%
Maximum [Member] | Secured Equipment Notes due in 2024 [Member]
Debt Instrument [Line Items]
Interest rate secured debt	3.59%
Maximum [Member] | Secured Equipment Notes due in 2021 [Member]
Debt Instrument [Line Items]
Interest rate secured debt	2.96%
Maximum [Member] | Secured Equipment Notes due in 2023 [Member]
Debt Instrument [Line Items]
Interest rate secured debt	4.20%
Maximum [Member] | Secured Equipment Notes due in 2022 [Member]
Debt Instrument [Line Items]
Interest rate secured debt	2.96%