Summary Of Preferred And Common Share Activity (Detail) (USD $)	12 Months Ended							12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Preferred Stock	Dec. 31, 2011 Preferred Stock	Dec. 31, 2010 Preferred Stock	Dec. 31, 2009 Preferred Stock	Dec. 31, 2012 Common Stock	Dec. 31, 2011 Common Stock	Dec. 31, 2010 Common Stock
Schedule of Capitalization, Equity [Line Items]
Balance, Preferred Stock, Issued, Beginning Balance				0	0	0	0
Balance, Preferred Stock, Issued, Ending Balance				0	0	0	0
Balance, Common Stock, Issued, Beginning Balance	112,312,123							112,312,123	119,812,123	125,812,123
Retirement of treasury stock, Issued								(6,500,000)	(7,500,000)	(6,000,000)
Balance, Common Stock, Issued, Ending Balance	105,812,123	112,312,123						105,812,123	112,312,123	119,812,123
Treasury Stock, beginning balance	(11,732,658)			0	0	0	0	(11,732,658)	(947,497)	(1,551,033)
Grants of restricted stock	149,720	173,553	121,923					69,720	173,553	121,923
Forfeitures of restricted stock									$ (7,153)	$ (10,621)
Issuance of common stock due to exercise of stock options, Treasury Stock	5,354,381	4,829,892	1,273,598					5,357,490	4,829,892	1,273,598
Treasury stock acquired								(11,771,039)	(23,281,453)	(6,781,364)
Retirement of treasury stock	6,500,000	7,500,000	6,000,000					6,500,000	7,500,000	6,000,000
Treasury Stock, ending balance	(11,576,487)	(11,732,658)		0	0	0	0	(11,576,487)	(11,732,658)	(947,497)