Consolidated Statements Of Stockholders' Equity (Parenthetical) - Quarter 1 Dividend Payment [Member] - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Regular dividends per share paid	$ 1.00	$ 1.00	$ 1.00
Extra dividends per share paid	$ 4.05	$ 3.05	$ 4.05