Condensed Consolidated Statements of Stockholders' Equity (Parenthetical) - $ / shares	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Statement of Stockholders' Equity [Abstract]
Cash dividends declared per common share (in dollars per share)	$ 0.39	$ 0.34
Common stock issued per share for stock bonus (in USD per share)	$ 44.26	$ 32.45