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	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Mann Group Promissory Notes | Note Payable Yield Changes 1
Fair Value Of Financial Instruments [Line Items]
Note payable, percentage of yield	31.0	29.0
Note payable, percentage of interest rate increases (decreases)	2.00%
Note payable to related party, fair value	$ 44.1	$ 46.2
Change in fair value of note payable value due to change in interest rate percentage	$ (2.1)
Increase (decrease) in fair value of note payable percentage due to increases (decreases) in interest rate percentage	(4.50%)
Mann Group Promissory Notes | Note Payable Yield Changes 2
Fair Value Of Financial Instruments [Line Items]
Note payable, percentage of yield	27.0	29.0
Note payable, percentage of interest rate increases (decreases)	(2.00%)
Note payable to related party, fair value	$ 48.5	$ 46.2
Change in fair value of note payable value due to change in interest rate percentage	$ 2.3
Increase (decrease) in fair value of note payable percentage due to increases (decreases) in interest rate percentage	5.00%
Mann Group Promissory Notes | Note Payable Yield Changes 3
Fair Value Of Financial Instruments [Line Items]
Note payable, percentage of yield	33.0	29.0
Note payable, percentage of interest rate increases (decreases)	4.00%
Note payable to related party, fair value	$ 42.2	$ 46.2
Change in fair value of note payable value due to change in interest rate percentage	$ (4.0)
Increase (decrease) in fair value of note payable percentage due to increases (decreases) in interest rate percentage	(8.70%)
Mann Group Promissory Notes | Note Payable Yield Changes 4
Fair Value Of Financial Instruments [Line Items]
Note payable, percentage of yield	25.0	29.0
Note payable, percentage of interest rate increases (decreases)	(4.00%)
Note payable to related party, fair value	$ 51.0	$ 46.2
Change in fair value of note payable value due to change in interest rate percentage	$ 4.8
Increase (decrease) in fair value of note payable percentage due to increases (decreases) in interest rate percentage	10.40%
Senior Notes | Note Payable Yield Changes 1
Fair Value Of Financial Instruments [Line Items]
Note payable, percentage of yield	31.0	29.0
Note payable, percentage of interest rate increases (decreases)	2.00%
Note payable to related party, fair value	$ 7.8	$ 8.0
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	(2.50%)
Senior Notes | Note Payable Yield Changes 2
Fair Value Of Financial Instruments [Line Items]
Note payable, percentage of yield	27.0	29.0
Note payable, percentage of interest rate increases (decreases)	(2.00%)
Note payable to related party, fair value	$ 8.2	$ 8.0
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	2.50%
Senior Notes | Note Payable Yield Changes 3
Fair Value Of Financial Instruments [Line Items]
Note payable, percentage of yield	33.0	29.0
Note payable, percentage of interest rate increases (decreases)	4.00%
Note payable to related party, fair value	$ 7.6	$ 8.0
Change in fair value of note payable value due to change in interest rate percentage	$ (0.4)
Increase (decrease) in fair value of note payable percentage due to increases (decreases) in interest rate percentage	(5.00%)
Senior Notes | Note Payable Yield Changes 4
Fair Value Of Financial Instruments [Line Items]
Note payable, percentage of yield	25.0	29.0
Note payable, percentage of interest rate increases (decreases)	(4.00%)
Note payable to related party, fair value	$ 8.4	$ 8.0
Change in fair value of note payable value due to change in interest rate percentage	$ 0.4
Increase (decrease) in fair value of note payable percentage due to increases (decreases) in interest rate percentage	5.00%
MidCap Credit Facility | Note Payable Yield Changes 1
Fair Value Of Financial Instruments [Line Items]
Note payable, percentage of yield	12.5	11.5
Note payable, percentage of interest rate increases (decreases)	1.00%
Note payable to related party, fair value	$ 39.0	$ 40.0
Change in fair value of note payable value due to change in interest rate percentage	$ (1.0)
Increase (decrease) in fair value of note payable percentage due to increases (decreases) in interest rate percentage	(2.50%)
MidCap Credit Facility | Note Payable Yield Changes 2
Fair Value Of Financial Instruments [Line Items]
Note payable, percentage of yield	10.5	11.5
Note payable, percentage of interest rate increases (decreases)	(1.00%)
Note payable to related party, fair value	$ 41.0	$ 40.0
Change in fair value of note payable value due to change in interest rate percentage	$ 1.0
Increase (decrease) in fair value of note payable percentage due to increases (decreases) in interest rate percentage	2.50%
MidCap Credit Facility | Note Payable Yield Changes 3
Fair Value Of Financial Instruments [Line Items]
Note payable, percentage of yield	13.5	11.5
Note payable, percentage of interest rate increases (decreases)	2.00%
Note payable to related party, fair value	$ 38.1	$ 40.0
Change in fair value of note payable value due to change in interest rate percentage	$ (1.9)
Increase (decrease) in fair value of note payable percentage due to increases (decreases) in interest rate percentage	(4.80%)
MidCap Credit Facility | Note Payable Yield Changes 4
Fair Value Of Financial Instruments [Line Items]
Note payable, percentage of yield	9.5	11.5
Note payable, percentage of interest rate increases (decreases)	(2.00%)
Note payable to related party, fair value	$ 42.1	$ 40.0
Change in fair value of note payable value due to change in interest rate percentage	$ 2.1
Increase (decrease) in fair value of note payable percentage due to increases (decreases) in interest rate percentage	5.30%