Fair Value of Financial Instruments - Fair Value Measurement of Debt Instruments Based on Discounted Cash Flow Model and Sensitive to Change in Yield (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($)
Mann Group Promissory Notes | Note Payable Yield Changes 1
Fair Value Of Financial Instruments [Line Items]
Note payable, percentage of yield	35.0
Note payable, percentage of interest rate increases (decreases)	2.00%
Note payable, percentage of hypothetical yield	37.0
Note payable to related party, fair value	$ 38.0
Note payable to related party, fair value after change	36.4
Change in fair value of note payable value due to change in interest rate percentage	$ (1.6)
Increase (decrease) in fair value of note payable percentage due to increases (decreases) in interest rate percentage	(4.20%)
Mann Group Promissory Notes | Note Payable Yield Changes 2
Fair Value Of Financial Instruments [Line Items]
Note payable, percentage of yield	35.0
Note payable, percentage of interest rate increases (decreases)	(2.00%)
Note payable, percentage of hypothetical yield	33.0
Note payable to related party, fair value	$ 38.0
Note payable to related party, fair value after change	39.8
Change in fair value of note payable value due to change in interest rate percentage	$ 1.8
Increase (decrease) in fair value of note payable percentage due to increases (decreases) in interest rate percentage	4.70%
Mann Group Promissory Notes | Note Payable Yield Changes 3
Fair Value Of Financial Instruments [Line Items]
Note payable, percentage of yield	35.0
Note payable, percentage of interest rate increases (decreases)	4.00%
Note payable, percentage of hypothetical yield	39.0
Note payable to related party, fair value	$ 38.0
Note payable to related party, fair value after change	34.8
Change in fair value of note payable value due to change in interest rate percentage	$ (3.2)
Increase (decrease) in fair value of note payable percentage due to increases (decreases) in interest rate percentage	(8.40%)
Mann Group Promissory Notes | Note Payable Yield Changes 4
Fair Value Of Financial Instruments [Line Items]
Note payable, percentage of yield	35.0
Note payable, percentage of interest rate increases (decreases)	(4.00%)
Note payable, percentage of hypothetical yield	31.0
Note payable to related party, fair value	$ 38.0
Note payable to related party, fair value after change	41.8
Change in fair value of note payable value due to change in interest rate percentage	$ 3.8
Increase (decrease) in fair value of note payable percentage due to increases (decreases) in interest rate percentage	10.00%
Senior Notes | Note Payable Yield Changes 1
Fair Value Of Financial Instruments [Line Items]
Note payable, percentage of yield	35.0
Note payable, percentage of interest rate increases (decreases)	2.00%
Note payable, percentage of hypothetical yield	37.0
Note payable to related party, fair value	$ 7.6
Note payable to related party, fair value after change	7.5
Change in fair value of note payable value due to change in interest rate percentage	$ (0.1)
Increase (decrease) in fair value of note payable percentage due to increases (decreases) in interest rate percentage	(1.30%)
Senior Notes | Note Payable Yield Changes 2
Fair Value Of Financial Instruments [Line Items]
Note payable, percentage of yield	35.0
Note payable, percentage of interest rate increases (decreases)	(2.00%)
Note payable, percentage of hypothetical yield	33.0
Note payable to related party, fair value	$ 7.6
Note payable to related party, fair value after change	7.8
Change in fair value of note payable value due to change in interest rate percentage	$ 0.2
Increase (decrease) in fair value of note payable percentage due to increases (decreases) in interest rate percentage	2.60%
Senior Notes | Note Payable Yield Changes 3
Fair Value Of Financial Instruments [Line Items]
Note payable, percentage of yield	35.0
Note payable, percentage of interest rate increases (decreases)	4.00%
Note payable, percentage of hypothetical yield	39.0
Note payable to related party, fair value	$ 7.6
Note payable to related party, fair value after change	7.4
Change in fair value of note payable value due to change in interest rate percentage	$ (0.2)
Increase (decrease) in fair value of note payable percentage due to increases (decreases) in interest rate percentage	(2.60%)
Senior Notes | Note Payable Yield Changes 4
Fair Value Of Financial Instruments [Line Items]
Note payable, percentage of yield	35.0
Note payable, percentage of interest rate increases (decreases)	(4.00%)
Note payable, percentage of hypothetical yield	31.0
Note payable to related party, fair value	$ 7.6
Note payable to related party, fair value after change	7.9
Change in fair value of note payable value due to change in interest rate percentage	$ 0.3
Increase (decrease) in fair value of note payable percentage due to increases (decreases) in interest rate percentage	3.90%
MidCap Credit Facility | Note Payable Yield Changes 1
Fair Value Of Financial Instruments [Line Items]
Note payable, percentage of yield	17.0
Note payable, percentage of interest rate increases (decreases)	1.00%
Note payable, percentage of hypothetical yield	18.0
Note payable to related party, fair value	$ 35.8
Note payable to related party, fair value after change	35.1
Change in fair value of note payable value due to change in interest rate percentage	$ (0.7)
Increase (decrease) in fair value of note payable percentage due to increases (decreases) in interest rate percentage	(2.00%)
MidCap Credit Facility | Note Payable Yield Changes 2
Fair Value Of Financial Instruments [Line Items]
Note payable, percentage of yield	17.0
Note payable, percentage of interest rate increases (decreases)	(1.00%)
Note payable, percentage of hypothetical yield	16.0
Note payable to related party, fair value	$ 35.8
Note payable to related party, fair value after change	36.6
Change in fair value of note payable value due to change in interest rate percentage	$ 0.8
Increase (decrease) in fair value of note payable percentage due to increases (decreases) in interest rate percentage	2.20%
MidCap Credit Facility | Note Payable Yield Changes 3
Fair Value Of Financial Instruments [Line Items]
Note payable, percentage of yield	17.0
Note payable, percentage of interest rate increases (decreases)	2.00%
Note payable, percentage of hypothetical yield	19.0
Note payable to related party, fair value	$ 35.8
Note payable to related party, fair value after change	34.3
Change in fair value of note payable value due to change in interest rate percentage	$ (1.5)
Increase (decrease) in fair value of note payable percentage due to increases (decreases) in interest rate percentage	(4.20%)
MidCap Credit Facility | Note Payable Yield Changes 4
Fair Value Of Financial Instruments [Line Items]
Note payable, percentage of yield	17.0
Note payable, percentage of interest rate increases (decreases)	(2.00%)
Note payable, percentage of hypothetical yield	15.0
Note payable to related party, fair value	$ 35.8
Note payable to related party, fair value after change	37.4
Change in fair value of note payable value due to change in interest rate percentage	$ 1.6
Increase (decrease) in fair value of note payable percentage due to increases (decreases) in interest rate percentage	4.50%