Consolidated Statements of Stockholders' Equity (Parenthetical) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Dividend per share to common stockholders (in dollars per share)	$ 1.20	$ 1.20	$ 1.20
Cumulative Dividends
Dividend per share to common stockholders (in dollars per share)	$ 1.20	$ 1.20	$ 1.20
Total Stockholders' Equity
Dividend per share to common stockholders (in dollars per share)	$ 1.20	$ 1.20	$ 1.20