Consolidated Statements Of Stockholders' Equity (Parenthetical) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Quarter 1 Dividend Payment [Member]	Dec. 31, 2012 Quarter 4 Dividend Payment [Member]
Regular dividends per share paid	$ 1.00	$ 1.00	$ 1.00	$ 1.00
Extra dividends per share paid	$ 7.25	$ 7.15	$ 5.00	$ 5.50