CONDENSED CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY (UNAUDITED) (Parenthetical)	3 Months Ended
Mar. 31, 2012	Mar. 31, 2011
Comprehensive income
Preferred stock dividends, (in hundredths)	5.00%	5.00%

The percentage rate used to calculate dividend payments on preferred stock.

No definition available.

Name:	us-gaap_PreferredStockDividendRatePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration