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Equity-Based Compensation - Additional Information (Detail)		1 Months Ended	12 Months Ended
	Jan. 01, 2020 shares	May 31, 2017	Dec. 31, 2019 USD ($) day $ / shares shares	Dec. 31, 2018 USD ($) $ / shares	Dec. 31, 2017 USD ($) $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant (in shares) | shares			16,050,000
Stock-based compensation expense			$ 33,607,000	$ 29,273,000	$ 26,534,000
Associated tax benefit			$ 7,800,000	6,800,000	6,300,000
Restricted stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			3 years
Stock-based compensation expense			$ 24,000,000.0	20,100,000	19,500,000
Fair value of awards vested			$ 14,600,000	$ 17,300,000	$ 22,000,000.0
Weighted average grant date fair value of awards granted (in dollars per share) | $ / shares			$ 6.61	$ 10.20	$ 15.03
Unrecognized expense			$ 27,000,000.0
Unrecognized expense recognition period			1 year 8 months 12 days
Performance share unit awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense			$ 9,000,000.0	$ 8,500,000	$ 6,700,000
Fair value of awards vested			$ 2,600,000	$ 5,300,000	$ 0
Weighted average grant date fair value of awards granted (in dollars per share) | $ / shares			$ 6.80	$ 12.71	$ 16.89
Unrecognized expense			$ 10,900,000
Unrecognized expense recognition period			2 years 7 months 6 days
Right to received shares of common stock | shares			1
Number of trading days | day			30
Performance share unit awards | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
PSU granted percentage of earnings (percent)			0.00%
Performance share unit awards | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
PSU granted percentage of earnings (percent)			200.00%
OMP GP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense			$ 200,000	$ 300,000	$ 200,000
OMP GP | Restricted unit awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		10 years
Percentage of outstanding units (percent)		9.00%
OMP LTIP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			1 year
OMP LTIP | Restricted unit awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense			$ 400,000	400,000	100,000
Fair value of awards vested			$ 300,000	$ 300,000	$ 0
Weighted average grant date fair value of awards granted (in dollars per share) | $ / shares			$ 18.57	$ 17.55	$ 17.00
Unrecognized expense			$ 10,000.00
Unrecognized expense recognition period			1 month 6 days
Long Term Incentive Plan (LTIP)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant (in shares) | shares			2,455,408
Increase in common units that can be issued as percentage of units outstanding (percent)			1.00%
Long Term Incentive Plan (LTIP) | Phantom units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair market value equivalent of number of OMP common units | shares			1
Stock-based compensation expense			$ 2,500,000	$ 500,000	$ 100,000
Fair value of awards vested			$ 800,000	$ 600,000	$ 0
Weighted average grant date fair value of awards granted (in dollars per share) | $ / shares			$ 18.57	$ 23.91	$ 16.40
Unrecognized expense recognition period			2 years
Vesting period			3 years
Unrecognized compensation cost			$ 4,300,000
Subsequent Event | OMP LTIP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional number of units authorized (shares) | shares	337,952

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