Consolidated Statements of Stockholders' Equity (Parenthetical) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Common stock transactions:
Stock options exercised	739,290
Common stock
Common stock transactions:
Common shares purchased and retired	388,101	25,677	18,351
Common shares issued	1,402,811	26,096	23,991
Non-vested common shares issued	148,278	120,873	122,912
Non-vested common shares forfeited	29,261	30,648	15,232
Stock options exercised	499,625	774,096	192,829
Shares tendered in payment of option price and income tax withholding amounts	239,665	392,411	183,805
Preferred Stock Including Additional Paid in Capital [Member]
Common stock transactions:
Stock Redeemed or Called During Period, Shares	0.00	0.00	5,000.00
Retained Earnings
Cash dividends declared:
Common (in dollars per share)		0.61	0.45
Preferred (in dollars per share)	0.00%	6.75%	6.75%