Consolidated Statements of Stockholders' Equity (USD $) In Thousands, unless otherwise specified	Total	Preferred Stock	Common Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning Balance at Dec. 31, 2011	$ 771,020	$ 50,000	$ 266,842	$ 435,144	$ 19,034
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	58,224	0	0	58,224	0
Other comprehensive loss, net of tax	(3,043)	0	0	0	(3,043)
Common stock transactions:
Common shares purchased and retired	263	0	(263)	0	0
Common shares issued	299	0	299	0	0
Non-vested common shares issued	0	0	0	0	0
Non-vested common shares forfeited or canceled	0	0	0	0	0
Stock options exercised, net of shares tendered in payment of option price and income tax withholding amounts	1,612	0	1,612	0	0
Tax benefit of stock-based compensation	360	0	360	0	0
Stock-based compensation expense	2,485	0	2,485	0	0
Stock Redeemed or Called During Period, Value	(50,000)	(50,000)	0	0	0
Cash dividends declared:
Common (per share)	(26,208)	0	0	(26,208)	0
Preferred (per share)	(3,300)	0	0	(3,300)	0
Ending Balance at Dec. 31, 2012	751,186	0	271,335	463,860	15,991
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	86,136	0	0	86,136	0
Other comprehensive loss, net of tax	(32,032)	0	0	0	(32,032)
Common stock transactions:
Common shares purchased and retired	(448)	0	(448)	0	0
Common shares issued	543	0	543	0	0
Non-vested common shares issued	0	0	0	0	0
Non-vested common shares forfeited or canceled	0	0	0	0	0
Stock options exercised, net of shares tendered in payment of option price and income tax withholding amounts	9,271	0	9,271	0	0
Tax benefit of stock-based compensation	1,898	0	1,898	0	0
Stock-based compensation expense	2,936	0	2,936	0	0
Cash dividends declared:
Common (per share)	(17,909)	0	0	(17,909)	0
Ending Balance at Dec. 31, 2013	801,581	0	285,535	532,087	(16,041)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	84,401	0	0	84,401	0
Other comprehensive loss, net of tax	13,507	0	0	0	13,507
Common stock transactions:
Common shares purchased and retired	(9,739)	0	(9,739)	0	0
Common shares issued	36,294	0	36,294	0	0
Non-vested common shares issued	0	0	0	0	0
Non-vested common shares forfeited or canceled	0	0	0	0	0
Stock options exercised, net of shares tendered in payment of option price and income tax withholding amounts	6,299	0	6,299	0	0
Tax benefit of stock-based compensation	2,193	0	2,193	0	0
Stock-based compensation expense	3,014	0	3,014	0	0
Cash dividends declared:
Common (per share)	(28,626)	0		(28,626)	0
Ending Balance at Dec. 31, 2014	$ 908,924	$ 0	$ 323,596	$ 587,862	$ (2,534)