Segment Information - Reconciliation of U.S. Gaap Income Before Income Taxes to Adjusted EBITDA (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting [Abstract]
Impairment charge recognized in non-recurring adjustment for royalty contracts	$ 0.8	$ 0.9	$ 1.0	$ 1.8
Income recognized in non-recurring adjustment for change in estimated legal expenses				$ 2.0