Consolidated Statements of Shareholders' Equity (Parenthetical) (USD $)	3 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012
Statement of Stockholders' Equity [Abstract]
Dividends per common share (in dollars per share)	$ 0.0625	$ 0.0625	$ 0.0625	$ 0.0625	$ 0.0575	$ 0.0575	$ 0.0575	$ 0.0575	$ 0.0425	$ 0.0425	$ 0.0425	$ 0.0425
Dividends per preferred share (in dollars per share)	$ 20.00	$ 20	$ 20	$ 20	$ 20	$ 20	$ 20	$ 20	$ 20.00	$ 20	$ 20	$ 20