Income Taxes - Attributes Available for Utilization (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
U.S. federal net operating losses [Member]
Operating Loss Carryforwards [Line Items]
Attribute amount	$ 2.6
First year of expiration	2023
U.S. state net operating losses [Member]
Operating Loss Carryforwards [Line Items]
Attribute amount	2,478.9
First year of expiration	2013
U.S. federal tax credits [Member]
Operating Loss Carryforwards [Line Items]
Attribute amount	35.3
First year of expiration	2020
U.S. state tax credits [Member]
Operating Loss Carryforwards [Line Items]
Attribute amount	7.8
First year of expiration	2013
Foreign net operating losses [Member]
Operating Loss Carryforwards [Line Items]
Attribute amount	$ 212.4
First year of expiration	2013