Change In Preferred Stock (Detail)	9 Months Ended					9 Months Ended			9 Months Ended			9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2011 5.75% Cummulative Convertible	Sep. 30, 2012 5.75% Cummulative Convertible	Dec. 31, 2011 5.75% Cummulative Convertible	Sep. 30, 2011 5.75% Cumulative Convertible Preferred Stock (Series A)	Sep. 30, 2012 5.75% Cumulative Convertible Preferred Stock (Series A)	Dec. 31, 2011 5.75% Cumulative Convertible Preferred Stock (Series A)	Sep. 30, 2011 4.50% Cumulative Convertible Preferred Stock	Sep. 30, 2012 4.50% Cumulative Convertible Preferred Stock	Dec. 31, 2011 4.50% Cumulative Convertible Preferred Stock	Sep. 30, 2011 5.00% Cumulative Convertible Preferred Stock (Series 2005B)	Sep. 30, 2012 5.00% Cumulative Convertible Preferred Stock (Series 2005B)	Dec. 31, 2011 5.00% Cumulative Convertible Preferred Stock (Series 2005B)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Preferred stock, shares outstanding, beginning period	7,251,515		1,500,000	1,497,000	1,497,000	1,100,000	1,100,000	1,100,000	2,559,000	2,559,000	2,559,000	2,096,000	2,096,000	2,096,000
Stock Issued During Period, Shares, Conversion of Convertible Securities	0	(111,111)	(3,000)			0			0			0
Preferred stock, shares outstanding, ending period	7,251,515		1,497,000	1,497,000	1,497,000	1,100,000	1,100,000	1,100,000	2,559,000	2,559,000	2,559,000	2,096,000	2,096,000	2,096,000
Conversion of Stock, Shares Converted	0	3,000
Interest rate			5.75%				5.75%			4.50%			5.00%