Parent Company Only Financial Information (Balance Sheets) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Assets:
Cash and interest bearing deposits	$ 168,054	$ 129,834	$ 62,572	$ 182,410
Trading securities	380	333
Securities available for sale	1,506,075	1,267,999
Other assets	84,832	75,392
TOTAL ASSETS	4,990,553	4,305,058
Liabilities and stockholders’ equity:
Short-term borrowings	224,626	270,081
Other borrowings	389,025	372,820
Accrued expenses and other liabilities	126,703	99,151
TOTAL LIABILITIES	4,586,014	3,952,165
Stockholders’ equity:
Common stock	16,828	16,612
Capital surplus	50,359	43,333
Retained earnings	236,279	198,182
Accumulated other comprehensive income	16,641	12,147
Treasury stock	0	(1,754)
TOTAL EQUITY	404,539	352,893	331,784	315,057
TOTAL LIABILITIES AND EQUITY	4,990,553	4,305,058
Parent
Assets:
Cash and interest bearing deposits	17,447	26,960	17,365	6,161
Trading securities	380	333
Securities available for sale	6,262	4,858
Investment in subsidiaries	517,256	460,946
Other assets	29,303	22,140
Due from subsidiaries	7,000	2,750
TOTAL ASSETS	577,648	517,987
Liabilities and stockholders’ equity:
Other borrowings	158,752	155,126
Accrued expenses and other liabilities	17,091	12,643
TOTAL LIABILITIES	175,843	167,769
Stockholders’ equity:
Preferred stock	81,698	81,698
Common stock	16,828	16,612
Capital surplus	50,359	43,333
Retained earnings	236,279	198,182
Accumulated other comprehensive income	16,641	12,147
Treasury stock	0	(1,754)
TOTAL EQUITY	401,805	350,218
TOTAL LIABILITIES AND EQUITY	$ 577,648	$ 517,987