Stockholders' Equity (Summarized Information about Warrants Outstanding) (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Class of Warrant or Right [Line Items]
Outstanding, ending balance	133,591	90,501
Stock Purchase Warrants 2010 Issuance [Member]
Class of Warrant or Right [Line Items]
Grant date	2010
Granted	51,627
Exercise price, lower limit	$ 20.64
Exercise price, upper limit	$ 27.41
Fair value of warrants issued	$ 351
Outstanding, ending balance	1,886	9,199
Stock Purchase Warrants 2011 Issuance [Member]
Class of Warrant or Right [Line Items]
Grant date	2011
Granted	9,324
Exercise price, lower limit	$ 27.53
Exercise price, upper limit	$ 33.14
Fair value of warrants issued	79
Outstanding, ending balance	9,324	9,324
Stock Purchase Warrants 2012 Issuance [Member]
Class of Warrant or Right [Line Items]
Grant date	2012
Granted	71,978
Exercise price, lower limit	$ 30.52
Exercise price, upper limit	$ 33.03
Fair value of warrants issued	628
Outstanding, ending balance	71,978	71,978
Stock Purchase Warrants 2014 Issuance [Member]
Class of Warrant or Right [Line Items]
Grant date	2014
Granted	50,403
Exercise price, lower limit	$ 45.62
Exercise price, upper limit	$ 49.06
Fair value of warrants issued	$ 276
Outstanding, ending balance	50,403