Executive Retirement and Exit Activities - Exit Activities (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 12, 2016 USD ($)
Restructuring and Related Activities [Abstract]
Separation Agreement, Consulting Fees	$ 0.3
Share-based Compensation Arrangement by Share-based Payment Award Accelerated Compensation Cost	$ 0.6
Restructuring and Related Cost, Number of Positions Eliminated		53
Severance and Termination Benefits Paid		$ 2.1
Severance and Termination Benefits		1.4
Retention Bonuses		$ 0.7
Liabilities Subject to Compromise, Early Contract Termination Fees			$ 1.7
Restructuring Reserve			$ 10.8