Consolidated Statement of Shareholders' Equity (Parenthetical) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Statement of Stockholders' Equity [Abstract]
Dividends, per share (in dollars per share)	$ 0.10	$ 0.090