Consolidated Statements of Changes in Stockholders' Equity and Comprehensive Income (Parenthetical) (Retained earnings, USD $)	12 Months Ended
Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Retained earnings
Dividends declared:
Common stock, dividends, per share in each period	$ 0.20	$ 0.20	$ 1.52

Aggregate dividends declared during the period for each share of common stock outstanding.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

Name:	us-gaap_CommonStockDividendsPerShareDeclared
Namespace Prefix:	us-gaap
Data Type:	us-types:perShareItemType
Balance Type:	na
Period Type:	duration