Income Taxes - Attributes Available for Utilization (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
U.S. federal net operating losses [Member]
Operating Loss Carryforwards [Line Items]
Attribute amount	$ 1.9
Deferred Tax Asset Attributes, First Year of Expiration	Dec. 31, 2023
U.S. state net operating losses [Member]
Operating Loss Carryforwards [Line Items]
Attribute amount	1,355.6
Deferred Tax Asset Attributes, First Year of Expiration	Dec. 31, 2015
U.S. federal tax credits [Member]
Operating Loss Carryforwards [Line Items]
Attribute amount	23.4
Deferred Tax Asset Attributes, First Year of Expiration	Dec. 31, 2021
U.S. state tax credits [Member]
Operating Loss Carryforwards [Line Items]
Attribute amount	5.9
Deferred Tax Asset Attributes, First Year of Expiration	Dec. 31, 2027
Foreign net operating losses [Member]
Operating Loss Carryforwards [Line Items]
Attribute amount	$ 297.0
Deferred Tax Asset Attributes, First Year of Expiration	Dec. 31, 2015