Consolidated Statements of Stockholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Common stock transactions:
Stock options exercised	350,438
Common stock
Common stock transactions:
Common shares purchased and retired	793,077	388,101	25,677
Common shares issued	21,414	1,402,811	26,096
Non-vested common shares issued	169,577	148,278	120,873
Non-vested common shares forfeited	19,184	29,261	30,648
Stock options exercised	350,438	499,625	774,096
Shares tendered in payment of option price and income tax withholding amounts	89,358	239,665	392,411
Preferred Stock Including Additional Paid in Capital [Member]
Common stock transactions:
Stock Redeemed or Called During Period, Shares	0.00	5,000.00	0.00
Retained Earnings
Cash dividends declared:
Common (in dollars per share)	$ 0.80	$ 0.64	$ 0.41
Preferred (in dollars per share)	0.00%	0.00%	0.00%