Notes Payable Convertible Senior Notes and Line of Credit - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Convertible Notes Payable	Oct. 31, 2009 Convertible Notes Payable
Debt Instrument [Line Items]
Principal payments on notes in 2014	$ 3.1
Principal payments on notes in 2015	2.1
Principal payments on notes in 2016	0.6
Convertible senior notes, aggregate principal amount					65.0
Convertible senior notes, interest rate					6.00%
Convertible senior notes, carrying amount				37.8
Convertible senior notes, conversion rate of shares issued				3,094,440
Convertible senior notes, conversion rate of shares issued				77.6398
Convertible senior notes, conversion price per share				$ 12.88
Convertible senior notes, conversion price dividend adjustment				$ 0.10
Notes payable, debt issuance cost	3.3
Notes payable, amortization of debt issuance costs	0.4	0.6	0.5
Notes payable, interest expense	2.0	4.2	4.2
Bank line of credit facility amount	$ 25.0
Bank line of credit facility, expiration date		2016-06