Condensed Parent Company Financial Statements (Balance Sheets) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Assets
Cash	$ 225,136	$ 253,408
Available-for-sale securities, at fair value	1,792,078	2,176,290
Loans, net of unearned income	14,409,398	12,896,602
Less: Allowance for loan losses	(91,705)	(96,922)	(107,351)
Goodwill	405,634	374,547
Total assets	20,010,727	18,097,783	17,519,613
Liabilities and Shareholders' Equity
Notes Payable	0	364
Subordinated notes	140,000	0	75,000
Other borrowings	196,465	255,104
Junior subordinated debentures	249,493	249,493
Shareholders' equity	2,069,822	1,900,589	1,804,705	1,543,533
Total liabilities and shareholders' equity	20,010,727	18,097,783
Reportable Legal Entities [Member] | Parent Company [Member]
Assets
Cash	151,303	80,869
Available-for-sale securities, at fair value	10,725	12,839
Investment in and receivable from subsidiaries	2,205,487	1,971,018
Loans, net of unearned income	3,993	3,768
Less: Allowance for loan losses	(972)	(81)
Net Loans	3,021	3,687
Goodwill	8,371	8,371
Other assets	119,739	113,930
Total assets	2,498,646	2,190,714
Liabilities and Shareholders' Equity
Other liabilities	20,509	21,292
Subordinated notes	140,000
Other borrowings	18,822	19,340
Junior subordinated debentures	249,493	249,493
Shareholders' equity	2,069,822	1,900,589
Total liabilities and shareholders' equity	$ 2,498,646	$ 2,190,714