Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015
Assets
Cash and due from banks	$ 205,973	$ 91,311	$ 178,985
Money market and other interest-earning investments	61,947	128,507	16,228
Total cash and cash equivalents	267,920	219,818	195,213
Trading securities - at fair value	4,838	3,941	3,995
Investment securities - available-for-sale, at fair value:
Total investment securities - available-for-sale	2,648,901	2,418,221	2,572,521
Investment securities - held-to-maturity, at amortized cost (fair value $939,855; $929,417; and $867,345, respectively)	865,957	872,111	823,255
Federal Home Loan Bank/Federal Reserve Bank stock, at cost	90,742	86,146	71,669
Loans held for sale ($44,422; $13,810; and $20,287, respectively at fair value)	44,422	13,810	217,667
Loans:
Commercial	1,893,700	1,804,615	1,775,954
Commercial real estate	2,943,525	1,847,821	1,767,341
Residential real estate	2,099,770	1,644,614	1,622,819
Consumer credit, net of unearned income	1,893,163	1,543,768	1,464,541
Covered loans, net of discount		107,587	135,407
Total loans	8,830,158	6,948,405	6,766,062
Allowance for loan losses	(51,804)	(51,296)	(48,479)
Allowance for loan losses - covered loans		(937)	(1,712)
Net loans	8,778,354	6,896,172	6,715,871
FDIC indemnification asset		9,030	16,475
Premises and equipment, net	231,656	196,676	131,336
Accrued interest receivable	79,536	69,098	66,605
Goodwill	655,523	584,634	588,464
Other intangible assets	44,237	35,308	40,996
Company-owned life insurance	350,193	341,294	337,802
Net deferred tax assets	179,448	109,984	127,622
Loan servicing rights	25,756	10,468	10,027
Assets held for sale	4,867	5,679	9,886
Other real estate owned and repossessed personal property	24,254	7,594	9,388
Other real estate owned - covered		4,904	4,753
Other assets	123,658	106,639	130,859
Total assets	14,420,262	11,991,527	12,074,404
Deposits:
Noninterest-bearing demand	2,883,917	2,488,855	2,557,665
Interest-bearing:
NOW	2,456,963	2,133,536	2,213,862
Savings	2,616,365	2,201,352	2,352,916
Money market	1,015,336	577,050	602,287
Time	1,479,021	1,000,067	1,082,840
Total deposits	10,451,602	8,400,860	8,809,570
Short-term borrowings	567,659	628,499	530,377
Other borrowings	1,367,896	1,291,747	1,067,993
Accrued expenses and other liabilities	221,988	179,251	209,741
Total liabilities	12,609,145	10,500,357	10,617,681
Shareholders' Equity
Preferred stock, 2,000 shares authorized, no shares issued or outstanding
Common stock, $1.00 per share stated value, 300,000 shares authorized, 135,005; 114,297; and 115,205 shares issued and outstanding, respectively	135,005	114,297	115,205
Capital surplus	1,342,393	1,087,911	1,098,384
Retained earnings	357,336	323,759	281,196
Accumulated other comprehensive income (loss), net of tax	(23,617)	(34,797)	(38,062)
Total shareholders' equity	1,811,117	1,491,170	1,456,723
Total liabilities and shareholders' equity	14,420,262	11,991,527	12,074,404
U.S. Treasury [Member]
Investment securities - available-for-sale, at fair value:
Total investment securities - available-for-sale	12,269	12,150	12,171
U.S. Government-Sponsored Entities and Agencies [Member]
Investment securities - available-for-sale, at fair value:
Total investment securities - available-for-sale	540,775	613,550	695,074
Mortgage-Backed Securities - Agency [Member]
Investment securities - available-for-sale, at fair value:
Total investment securities - available-for-sale	1,336,605	1,066,361	1,104,145
States and Political Subdivisions [Member]
Investment securities - available-for-sale, at fair value:
Total investment securities - available-for-sale	417,163	387,296	388,039
Other Debt Securities Including Pooled Trust Preferred Securities [Member]
Investment securities - available-for-sale, at fair value:
Total investment securities - available-for-sale	$ 342,089	$ 338,864	$ 373,092