Consolidated Statements of Stockholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Regular Dividend
Dividend on common stock, per share	$ 2.16	$ 2.04	$ 1.97
Special Dividend
Dividend on common stock, per share			$ 6.66