Note 9. Shareholders' Equity (Detail) (USD $)	1 Months Ended			3 Months Ended		5 Months Ended	7 Months Ended	12 Months Ended				36 Months Ended				12 Months Ended						1 Months Ended	12 Months Ended					3 Months Ended	12 Months Ended		1 Months Ended		3 Months Ended	12 Months Ended		1 Months Ended				12 Months Ended	1 Months Ended	12 Months Ended
	Oct. 31, 2011	Feb. 28, 2011	Feb. 28, 2009	Dec. 31, 2011	Dec. 31, 2008	May 31, 2011	Dec. 31, 2009	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2011	Jan. 31, 2011	Jun. 30, 2010	May 31, 2010	Dec. 31, 2011 Non-Employee Directors Stock Plan [Member]	Dec. 31, 2010 Non-Employee Directors Stock Plan [Member]	Dec. 31, 2009 Non-Employee Directors Stock Plan [Member]	Dec. 31, 2011 Stock Award Plans [Member]	Dec. 31, 2010 Stock Award Plans [Member]	Dec. 31, 2009 Stock Award Plans [Member]	Jun. 30, 2009 Private Placement [Member]	Dec. 31, 2008 Series 1 [Member]	Dec. 31, 2011 Warrants Exercised [Member]	Dec. 31, 2010 Granted Without Vesting Requirements [Member]	Dec. 31, 2009 Granted Without Vesting Requirements [Member]	Dec. 31, 2011 Units Vesting in June 2012 [Member]	Sep. 30, 2008 Series B Preferred Stock [Member]	Dec. 31, 2010 Series B Preferred Stock [Member]	Dec. 31, 2011 Series B Preferred Stock [Member]	Jan. 31, 2011 Mandatory Convertible Preferred Stock [Member]	Sep. 29, 2008 Mandatory Convertible Preferred Stock [Member]	Sep. 30, 2008 Mandatory Convertible Preferred Stock [Member]	Dec. 31, 2011 Mandatory Convertible Preferred Stock [Member]	Dec. 31, 2010 Mandatory Convertible Preferred Stock [Member]	Oct. 31, 2009 Twelve Percent Convertible Preferred Stock [Member]	Jul. 31, 2009 Twelve Percent Convertible Preferred Stock [Member]	Feb. 28, 2009 Twelve Percent Convertible Preferred Stock [Member]	Dec. 31, 2011 Units Vesting in March 2014 [Member]	Dec. 31, 2008 Series 2 [Member]	Feb. 28, 2009 Series 3 [Member]	Dec. 31, 2011 Stock Options [Member]	Dec. 31, 2010 Stock Options [Member]	Dec. 31, 2009 Stock Options [Member]	Dec. 31, 2011 Stock Units [Member]
Common Stock, Shares Authorized				500,000,000				500,000,000	400,000,000			500,000,000			400,000,000
Common Stock, Par or Stated Value Per Share (in Dollars per share)				$ 0.25				$ 0.25	$ 0.25			$ 0.25
Common Stock Issued				285,682,569				285,682,569				285,682,569
Common Stock, Dividends, Per Share, Declared (in Dollars per share)		$ 0.0125		$ 0.02
Total Dividends Declared (in Dollars)				$ 5,600,000
Average Realized Silver Price (in Dollars)				37.02
Dividends, Common Stock (in Dollars)		3,600,000						(5,592,000)
Stock Issued During Period, Value, New Issues (in Dollars)							43,393,000															60,000,000		5,300,000														4,300,000
Stock Issued During Period, Shares, New Issues			32,000,000		34,400,000		17,391,302				10,200,000											17,400,000		2,100,000														42,621
Class of Warrant or Right, Outstanding							12,173,913			12,173,913												12.2
Class of Warrant or Right, Exercise Price of Warrants or Rights																						3.68
Common Stock And Warrants Price																						3.45
Proceeds from Issuance of Private Placement (in Dollars)																						57,600,000
Share-based Goods and Nonemployee Services Transaction, Valuation Method, Risk Free Interest Rate																						1.99%
Share-based Goods and Nonemployee Services Transaction, Valuation Method, Expected Volatility Rate																						131.00%
Share-based Goods and Nonemployee Services Transaction, Valuation Method, Expected Dividend Rate																						0.00%
Warrants Issued To Purchase Common Stock																							8.1																	7,700,000	18,400,000
Common Stock And Warrants Issued			36,800,000
Proceeds from Warrant Exercises (in Dollars)	1,000,000							5,786,000	53,093,000			10,500,000												5,300,000
Preferred Stock, Shares Authorized				5,000,000				5,000,000	5,000,000			5,000,000
Preferred Stock, Par or Stated Value Per Share (in Dollars per share)				$ 0.25				$ 0.25				$ 0.25																	$ 0.25	$ 0.25				$ 0.25	$ 0.25
Preferred Stock, Shares Outstanding													157,814																157,816	157,816				0	2,012,500
Conversion of Stock, Shares Converted																															2,012,500
Debt Instrument, Convertible, Conversion Ratio																																		9.3773
Stock Issued During Period, Shares, Conversion of Convertible Securities																																		18,900,000		1,801,171	828,326
Preferred Stock Shares Converted																																				28,921	13,700
Preferred Stock, Dividend Rate, Per-Dollar-Amount (in Dollars per share)																													$ 3.50
Preferred Stock, Dividends, Per Share, Cash Paid (in Dollars per share)																												$ 0.875
Preferred Stock, Dividend Rate, Percentage																																	6.50%
Temporary Equity, Liquidation Preference Per Share (in Dollars per share)																																			$ 100,000,000
Preferred Stock, Dividends Per Share, Declared (in Dollars per share)																																$ 1.625
Dividends, Preferred Stock, Stock (in Dollars)									22,891,000																							3,270,000
Preferred Stock, Redemption Price Per Share (in Dollars per share)				$ 50				$ 50				$ 50
Preferred Stock, Liquidation Preference Per Share (in Dollars per share)				$ 50				$ 50				$ 50																							$ 100
undefined (in Dollars)																													8,581,000	7,891,000				0	201,250,000
Preferred Stock Conversion Price (in Dollars per share)																														$ 15.55
Preferred Stock Conversion Rate																														3.2154				9.3773
Conversion Of Convertible Preferred Stock To Common Stock (in Dollars)																																		18,900,000
Share-based Compensation (in Dollars)								2,073,000	3,446,000	2,746,000									2,100,000	3,400,000	2,700,000																								500,000
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized (in Dollars)				2,200,000				2,200,000				2,200,000							1,500,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized														20,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant				19,696,320				19,696,320				19,696,320				671,061
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period																22,884	48,825	22,568
Allocated Share-based Compensation Expense (in Dollars)								147,000	263,000							194,000	168,000	84,000
Stock Issued During Period, Shares, Share-based Compensation, Gross																19,752	33,068
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures									352,517	559,685															322,854	559,685
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value (in Dollars)				600,000				600,000				600,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Total Intrinsic Value (in Dollars)																																										600,000	1,500,000	22,000
Proceeds from Stock Options Exercised (in Dollars)								500,000	3,400,000	36,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number				561,276				561,276	388,501			561,276															248,010												161,591
Employee Benefits and Share-based Compensation (in Dollars)												1,500,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period						314,826		(314,826)
Stock Repurchased During Period, Shares								56,688
Stock Repurchased During Period, Value (in Dollars)								$ 500,000
Treasury Stock Acquired, Average Cost Per Share (in Dollars per share)								$ 8.28