Related Party Transactions - Additional Information (Detail) - USD ($) $ in Millions |
1 Months Ended | ||||||
|---|---|---|---|---|---|---|---|
Apr. 26, 2017 |
May 31, 2019 |
Nov. 30, 2018 |
Mar. 31, 2017 |
Dec. 31, 2019 |
Dec. 31, 2018 |
Apr. 30, 2017 |
|
| Related Party Transaction [Line Items] | |||||||
| Unpaid principal balance of convertible senior note due to related parties | $ 3 | $ 3 | |||||
| Chief Executive Officer [Member] | |||||||
| Related Party Transaction [Line Items] | |||||||
| Common stock shares issued | 102,880 | 95,420 | |||||
| Issuance of common stock public offering price | $ 25 | $ 25 | |||||
| Chief Executive Officer [Member] | Private Placement [Member] | |||||||
| Related Party Transaction [Line Items] | |||||||
| Common stock shares issued | 56,915 | ||||||
| Issuance of common stock public offering price | $ 20 | ||||||
| Chief Executive Officer [Member] | Zero-Coupon Convertible Senior Notes due in 2020 [Member] | Recourse debt [Member] | |||||||
| Related Party Transaction [Line Items] | |||||||
| Principal amount of convertible senior notes | $ 10 | ||||||
| Convertible instrument, shares issued | 33,333 | ||||||
| Conversion feature of Convertible Senior Notes | $ 10 | ||||||