Income Taxes - Attributes Available for Utilization (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($)
U.S. state net operating losses [Member]
Operating Loss Carryforwards [Line Items]
Attribute amount	$ 1,203.6
Deferred Tax Asset Attributes, First Year of Expiration	Dec. 31, 2019
U.S. state tax credits [Member]
Operating Loss Carryforwards [Line Items]
Attribute amount	$ 2.2
Deferred Tax Asset Attributes, First Year of Expiration	Dec. 31, 2020
Foreign net operating losses [Member]
Operating Loss Carryforwards [Line Items]
Attribute amount	$ 369.3	[1]
Deferred Tax Asset Attributes, First Year of Expiration	Dec. 31, 2019

[1] (a) Includes approximately $265.9 of net operating loss carryforwards in Luxembourg as of December 31, 2018.