Consolidated Statements of Changes in Stockholders Equity (Unaudited) (USD $) In Thousands, unless otherwise specified	Total	Common stock	Retained earnings	Accumulated other comprehensive income
Beginning Balance at Dec. 31, 2012	$ 751,186	$ 271,335	$ 463,860	$ 15,991
Comprehensive income:
Net income	65,361	0	65,361	0
Other comprehensive income, net of tax	(23,939)	0	0	(23,939)
Common stock transactions:
Common shares purchased and retired 387,967 and 25,677 in 2014 and 2013, respectively	(448)	(448)	0	0
Common shares issued 1,402,811 in 2014 and 26,096 in 2013	543	543	0	0
Non-vested common shares issued 147,876 and 120,873 in 2014 and 2013 respectively	0	0	0	0
17,741 and 10,517 non-vested common shares forfeited in 2014 and 2013 respectively	0	0	0	0
372,880 and 688,864 stock options exercised, net of 166,780 and 336,442 shares tendered in payment of option price and income tax withholding amounts in 2014 and 2013 respectively	8,137	8,137	0	0
Tax benefit of stock-based compensation	1,578	1,578	0	0
Stock-based compensation expense	2,207	2,207	0	0
Cash dividends declared:
Common ($0.48 per share) in 2014 and ($0.27 per share) in 2013	(11,765)	0	(11,765)	0
Ending Balance at Sep. 30, 2013	792,860	283,352	517,456	(7,948)
Beginning Balance at Dec. 31, 2013	801,581	285,535	532,087	(16,041)
Comprehensive income:
Net income	61,625	0	61,625	0
Other comprehensive income, net of tax	8,411	0	0	8,411
Common stock transactions:
Common shares purchased and retired 387,967 and 25,677 in 2014 and 2013, respectively	(9,736)	(9,736)	0	0
Common shares issued 1,402,811 in 2014 and 26,096 in 2013	35,972	35,972	0	0
Non-vested common shares issued 147,876 and 120,873 in 2014 and 2013 respectively	0	0	0	0
17,741 and 10,517 non-vested common shares forfeited in 2014 and 2013 respectively	0	0	0	0
372,880 and 688,864 stock options exercised, net of 166,780 and 336,442 shares tendered in payment of option price and income tax withholding amounts in 2014 and 2013 respectively	4,914	4,914	0	0
Tax benefit of stock-based compensation	1,541	1,541	0	0
Stock-based compensation expense	2,906	2,906	0	0
Cash dividends declared:
Common ($0.48 per share) in 2014 and ($0.27 per share) in 2013	(21,350)	0	(21,350)	0
Ending Balance at Sep. 30, 2014	$ 885,864	$ 321,132	$ 572,362	$ (7,630)