Stockholders' Equity (Summarized Information about Warrants Outstanding) (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Class of Warrant or Right [Line Items]
Outstanding, ending balance	117,929	197,783
Stock purchase warrants 2011 issuance
Class of Warrant or Right [Line Items]
Grant date	2011
Warrants issued	9,324
Exercise price, lower limit	$ 27.53
Exercise price, upper limit	$ 33.14
Fair value of warrants issued	$ 79
Outstanding, ending balance		6,226
Stock Purchase Warrants 2012 Issuance
Class of Warrant or Right [Line Items]
Grant date	2012
Warrants issued	71,978
Exercise price, lower limit	$ 30.52
Exercise price, upper limit	$ 33.03
Fair value of warrants issued	$ 628
Outstanding, ending balance	6,625	49,975
Stock Purchase Warrants 2014 Issuance [Member]
Class of Warrant or Right [Line Items]
Grant date	2014
Warrants issued	50,403
Exercise price, lower limit	$ 45.62
Exercise price, upper limit	$ 49.06
Fair value of warrants issued	$ 276
Outstanding, ending balance	14,365	50,403
Stock Purchase Warrants 2015 Issuance [Member]
Class of Warrant or Right [Line Items]
Grant date	2015
Warrants issued	91,179
Exercise price, lower limit	$ 42.45
Exercise price, upper limit	$ 54.48
Fair value of warrants issued	$ 1,333
Outstanding, ending balance	86,495	91,179
Stock Purchase Warrants 2016 Issuance [Member]
Class of Warrant or Right [Line Items]
Grant date	2016
Warrants issued	10,444
Exercise price, lower limit	$ 63.33
Exercise price, upper limit	$ 77.33
Fair value of warrants issued	$ 189
Outstanding, ending balance	10,444