Income Per Share - Additional Information (Detail) (USD $) In Thousands, except Share data in Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share [Line Items]
Effect of dilutive stock-based compensation awards		0.7		0.7
Stock-based compensation awards outstanding	0.2	0.8	0.1	0.9
Effect of Potentially Issuable Shares		4.0		2.7
Approximate number of common stock share which can be purchased under warrants	14.1		14.1
Adjusted strike price under warrant	25.96		25.96
Effect of potentially issuable shares under warrants		2.1		0.6
Loss on call spread modification related to convertible notes			$ 4,869
3.75% Convertible Senior Notes [Member]
Earnings Per Share [Line Items]
Interest rate of Senior Notes	3.75%		3.75%
Maturity year of note			2014
Adjusted strike price under warrant	25.96		25.96