Consolidated Statement of Changes in Stockholders' Equity (Parenthetical) - $ / shares	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Common stock
Common stock transactions:
Common shares purchased and retired	23,960	22,727
Common shares issued	3,848,929	11,267,676
Non-vested common shares issued	210,039	134,044
Non-vested common shares forfeited	40,122	30,070
Stock options exercised (in shares)	148,834	180,789
Shares tendered in payment of option price and income tax withholding amounts	28,194	56,082
Retained earnings
Common stock transactions:
Common dividends (in dollars per share)	$ 0.84	$ 0.72