Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) - $ / shares	3 Months Ended				12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Stockholders' Equity [Abstract]
Cash dividends declared per common share (in $ per share)	$ 0.45	$ 0.45	$ 0.45	$ 0.45	$ 1.80	$ 1.8	$ 1.8
Cash dividends declared per preferred share (in $ per share)	$ 1.8125	$ 1.8125	$ 1.8125	$ 1.8125	$ 7.25	$ 0	$ 0