Income Taxes Computed at Federal Statutory Rate (Detail) - USD ($) $ in Thousands	3 Months Ended								9 Months Ended	12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income from continuing operations before taxes	$ (46,545)	$ (33,153)	$ 101,564	$ 3,288	$ (36,925)	$ (11,421)	$ 82,783	$ 28,670	$ 34,400	$ 25,154	$ 63,107	$ 47,276
Provision for income taxes:
Tax at Federal statutory rate										5,282	17,266	16,546
Effect of the tax reform on deferred taxes											(11,101)
Impact of Partnership loss not subject to federal income taxes											53	741
State taxes net of federal benefit										1,626	1,864	3,170
Permanent differences										345	99	89
Change in valuation allowance net of effect of the tax reform										23	107	115
Other										241	(686)	(285)
Income tax expense										$ 7,517	$ 7,602	$ 20,376