Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Operating Activities
Net cash provided by operating activities	$ 152,956	$ 158,495
Investing Activities
Proceeds from sales, maturities and prepayments of investment securities, available-for-sale	1,397,533	670,810
Purchase of investment securities, available-for-sale	(1,873,893)	(1,171,083)
Principal collected on loans	706,240	678,236
Loans originated or acquired	(716,729)	(577,733)
Net addition of premises and equipment and other real estate owned	(7,896)	(13,560)
Proceeds from sale of other real estate owned	28,483	31,356
Net (purchase) sale of non-marketable equity securities	(664)	15,357
Net cash used in investment activities	(466,926)	(366,617)
Financing Activities
Net increase in deposits	381,884	248,626
Net increase in securities sold under agreements to repurchase	156,193	52,417
Net decrease in Federal Home Loan Bank advances	(152,025)	(76,088)
Net increase in federal funds purchased and other borrowed funds	264	39,894
Cash dividends paid	(28,052)	(28,047)
Excess tax deficiencies from stock options exercised	(8)	0
Proceeds from stock options exercised	81	0
Net cash provided by financing activities	358,337	236,802
Net increase in cash and cash equivalents	44,367	28,680
Cash and cash equivalents at beginning of period	128,032	105,091
Cash and cash equivalents at end of period	172,399	133,771
Supplemental Disclosure of Cash Flow Information
Cash paid during the period for interest	28,721	35,850
Cash paid during the period for income taxes	18,081	6,319
Sale and refinancing of other real estate owned	1,578	4,333
Transfer of loans to other real estate owned	$ 21,029	$ 64,478