Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011	Dec. 31, 2010
Cash Flows From Operating Activities
Net income	$ 21,723	$ 16,433
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation	2,295	2,555
Amortization and impairment of other intangible assets	2,021	1,924
Net premium amortization on investment securities	3,728	2,006
Accretion of FDIC indemnification asset	(4,764)	0
Stock compensation expense	499	777
Provision for loan losses	2,056	3,312
Net securities gains	(619)	(1,499)
Impairment on available-for-sale securities	96	299	1,409	3,927
Gain on sale leasebacks	(1,607)	(1,636)
Gain on derivatives	(182)	(332)
Net gains on sales of loans	(374)	(576)
Increase in cash surrender value of company owned life insurance	(1,471)	(1,145)
Residential real estate loans originated for sale	(12,003)	(21,757)
Proceeds from sale of residential real estate loans	13,022	29,336
Decrease in interest receivable	2,520	2,563
Decrease in other real estate owned	6,383	539
Decrease in other assets	5,911	2,212
Increase (decrease) in accrued expenses and other liabilities	(25,691)	21,988
Total adjustments	(8,180)	40,566
Net cash flows provided by operating activities	13,543	56,999
Cash Flows From Investing Activities
Cash and cash equivalents of acquired banks	0	83,604
Purchases of investment securities available-for-sale	(290,983)	(141,503)
Proceeds from maturities, prepayments and calls of investment securities available-for-sale	100,032	144,367
Proceeds from sales of investment securities available-for-sale	13,423	54,356
Proceeds from maturities, prepayments and calls of investment securities held-to-maturity	11,157	36,108
Proceeds from sale of loans	782	4,624
Reimbursements under FDIC loss share agreements	19,221	0
Net principal collected from (loans made to) customers	98,983	(7,780)
Proceeds from sale of premises and equipment and other assets	3	168
Purchases of premises and equipment and other assets	(3,475)	(712)
Net cash flows provided by (used in) investing activities	(50,857)	173,232
Cash Flows From Financing Activities
Deposits	56,214	(57,057)
Short-term borrowings	(72,091)	13,498
Payments for maturities on other borrowings	(104)	(98)
Payments related to retirement of debt	0	(18,333)
Cash dividends paid on common stock	(8,510)	(6,630)
Common stock repurchased	(686)	(331)
Proceeds from exercise of stock options, including tax benefit	0	90
Common stock issued	60	56
Net cash flows used in financing activities	(25,117)	(68,805)
Net increase (decrease) in cash and cash equivalents	(62,431)	161,426
Cash and cash equivalents at beginning of period	222,872	251,552	251,552
Cash and cash equivalents at end of period	160,441	412,978	222,872	251,552
Supplemental cash flow information:
Total interest paid	10,608	12,724
Total taxes paid (net of refunds)	$ 2,600	$ 0