Consolidated Statement of Stockholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Consolidated Statement of Stockholders' Equity
Dividends accrued, per share (in dollars per share)	$ 1.75	$ 1.45	$ 1.18