Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating Activities:
Net Income	$ 51,008	$ 43,050	$ 23,090
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses	18,500	26,000	45,600
Gains on sales of loans	(9,645)	(5,017)	(5,986)
Proceeds from sales of loans	314,521	224,341	281,511
Loans originated for sale	(303,723)	(217,663)	(286,317)
Proceeds from sale of trading securities	0	0	1,083
Net gains on sales of other real estate and repossessed assets	(1,532)	(2,208)	(1,394)
Net loss on disposal of premises and equipment and branch bank properties	0	616	865
Depreciation of premises and equipment	8,142	7,950	7,826
Amortization of intangible assets	3,969	3,615	3,609
Net amortization of premiums and discounts on investment securities	4,795	4,024	2,818
Share-based compensation expense	1,865	1,517	1,395
Deferred income tax	12,668	6,413	3,439
Contributions to defined benefit pension plan	(12,000)	0	(10,000)
Net decrease in interest receivable and other assets	4,261	10,747	350
Net increase (decrease) in interest payable and other liabilities	2,337	(909)	9,325
Net Cash Provided by Operating Activities	95,166	102,476	77,214
Investment securities-available-for-sale:
Proceeds from maturities, calls and principal reductions	268,848	327,013	333,878
Purchases	(191,689)	(419,714)	(253,815)
Investment securities-held-to-maturity:
Proceeds from maturities, calls and principal reductions	55,352	52,115	47,150
Purchases	(102,034)	(70,014)	(81,346)
Net increase in loans	(330,760)	(196,484)	(124,985)
Proceeds from sales of other real estate and repossessed assets	24,341	19,202	18,066
Purchases of premises and equipment, net	(10,303)	(8,602)	(7,733)
Purchase of bank owned life insurance	0	(3,600)	0
Cash acquired, net of cash paid, in business combinations	339,372	0	17,177
Net Cash Provided by (Used in) Investing Activities	53,127	(300,084)	(51,608)
Financing Activities:
Net increase in interest- and noninterest-bearing demand deposits and savings accounts	307,972	113,164	200,829
Net increase (decrease) in time deposits	(157,425)	(78,072)	19,570
Net increase in short-term borrowings	6,677	61,083	2,135
Repayment of FHLB advances	(8,768)	(31,073)	(51,733)
Cash dividends paid	(22,566)	(21,964)	(21,243)
Proceeds from directors’ stock plans and exercise of stock options	260	245	292
Shares issued, net of shares withheld, for restricted stock performance units	(248)	0	0
Net Cash Provided by Financing Activities	125,902	43,383	149,850
Net Increase (Decrease) in Cash and Cash Equivalents	274,195	(154,225)	175,456
Cash and Cash Equivalents at Beginning of Year	381,940	536,165	360,709
Cash and Cash Equivalents at End of Year	656,135	381,940	536,165
Supplemental Disclosure of Cash Flow Information:
Interest paid	23,859	32,129	40,206
Federal income taxes paid	9,029	7,787	9,800
Loans transferred to other real estate and repossessed assets	15,794	19,664	26,429
Business Combinations
Fair value of tangible assets acquired (noncash)	52,337	0	749,916
Goodwill and identifiable intangible assets acquired	12,350	0	53,310
Liabilities assumed	404,059	0	736,706
Common stock and stock options issued	$ 0	$ 0	$ 83,697