Loans and Leases (Details 7	3 Months Ended
	Mar. 31, 2016 USD ($) Contract	Mar. 31, 2015 USD ($) Contract		Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Financing Receivable, Modifications [Line Items]
Allowance for loan and lease losses	$ 130,361,000			$ 115,111,000
Financing Receivables, Impaired, Troubled Debt Restructuring, Write-down	$ 0	$ 772,000
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | Contract	1	3
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	$ 230,000	$ 1,904,000	[1],[2]
Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Modifications [Line Items]
Allowance for loan and lease losses	120,807,000	79,680,000		105,534,000	$ 70,456,000
Allowance for Loan and Lease Losses, Write-offs	(5,373,000)	(9,911,000)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	1,481,000	2,531,000
Provision for Loan and Lease Losses	19,165,000	16,604,000
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	30,040,000	12,226,000
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	90,767,000	67,454,000
Financing Receivable, Individually Evaluated for Impairment	196,491,000	175,309,000
Financing Receivable, Collectively Evaluated for Impairment	14,110,470,000	11,842,572,000
Loans and Leases Receivable, Net of Deferred Income	14,306,961,000	12,017,881,000		14,289,209,000
Purchased Credit Impaired Loans and Leases
Financing Receivable, Modifications [Line Items]
Allowance for loan and lease losses	9,554,000			9,577,000
Loans and Leases Receivable, Allowance, Covered	9,554,000	12,698,000		9,577,000	13,999,000
Allowance for Loan and Lease Losses, Write-offs	(163,000)	(579,000)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	0	11,000
Provision for Loan and Lease Losses	140,000	(733,000)
Receivables Acquired With Deteriorated Credit Quality, Allowance For Credit Losses	9,554,000	12,698,000
Receivables Acquired with Deteriorated Credit Quality	176,556,000	254,285,000
Loans and Leases Receivable, Net of Deferred Income	176,556,000	254,285,000		189,045,000
NonPCI and PCI Loans
Financing Receivable, Modifications [Line Items]
Allowance for loan and lease losses	130,361,000			115,111,000
Loans and Leases Receivable Allowance Covered And Noncovered	130,361,000	92,378,000		115,111,000	84,455,000
Allowance for Loan and Lease Losses, Write-offs	(5,536,000)	(10,490,000)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	1,481,000	2,542,000
Provision for Loan and Lease Losses	19,305,000	15,871,000
Loans and Leases Receivable, Net of Deferred Income	14,483,517,000			14,478,254,000
Loans and Leases Receivable Net Of Deferred Income Covered And Noncovered	14,483,517,000	12,272,166,000
Consumer Portfolio Segment | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Modifications [Line Items]
Allowance for loan and lease losses	875,000	802,000		661,000	1,253,000
Allowance for Loan and Lease Losses, Write-offs	(591,000)	(63,000)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	16,000	194,000
Provision for Loan and Lease Losses	789,000	(582,000)
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	163,000	178,000
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	712,000	624,000
Financing Receivable, Individually Evaluated for Impairment	1,102,000	3,729,000
Financing Receivable, Collectively Evaluated for Impairment	109,520,000	89,946,000
Loans and Leases Receivable, Net of Deferred Income	$ 110,622,000	$ 93,675,000		120,849,000
Commercial Portfolio Segment | Asset Based
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | Contract	0	1
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	$ 0	$ 385,000
Commercial Portfolio Segment | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Modifications [Line Items]
Allowance for loan and lease losses	83,957,000	45,794,000		61,082,000	39,858,000
Allowance for Loan and Lease Losses, Write-offs	(4,045,000)	(8,395,000)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	314,000	410,000
Provision for Loan and Lease Losses	26,606,000	13,921,000
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	27,902,000	10,493,000
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	56,055,000	35,301,000
Financing Receivable, Individually Evaluated for Impairment	96,614,000	103,208,000
Financing Receivable, Collectively Evaluated for Impairment	7,893,955,000	5,903,859,000
Loans and Leases Receivable, Net of Deferred Income	7,990,569,000	6,007,067,000		7,952,577,000
Commercial Portfolio Segment | Non Purchased Credit Impaired Loans and Leases | Asset Based
Financing Receivable, Modifications [Line Items]
Loans and Leases Receivable, Net of Deferred Income	2,588,916,000			2,547,533,000
Real Estate Construction | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Modifications [Line Items]
Allowance for loan and lease losses	6,876,000	2,173,000		7,137,000	4,248,000
Allowance for Loan and Lease Losses, Write-offs	0	0
Allowance for Loan and Lease Loss, Recovery of Bad Debts	152,000	632,000
Provision for Loan and Lease Losses	(413,000)	(2,707,000)
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	21,000	55,000
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	6,855,000	2,118,000
Financing Receivable, Individually Evaluated for Impairment	7,945,000	8,639,000
Financing Receivable, Collectively Evaluated for Impairment	567,528,000	320,070,000
Loans and Leases Receivable, Net of Deferred Income	575,473,000	328,709,000		527,720,000
Mortgage Loans on Real Estate | Non Purchased Credit Impaired Loans and Leases
Financing Receivable, Modifications [Line Items]
Allowance for loan and lease losses	29,099,000	30,911,000		36,654,000	$ 25,097,000
Allowance for Loan and Lease Losses, Write-offs	(737,000)	(1,453,000)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	999,000	1,295,000
Provision for Loan and Lease Losses	(7,817,000)	5,972,000
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	1,954,000	1,500,000
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	27,145,000	29,411,000
Financing Receivable, Individually Evaluated for Impairment	90,830,000	59,733,000
Financing Receivable, Collectively Evaluated for Impairment	5,539,467,000	5,528,697,000
Loans and Leases Receivable, Net of Deferred Income	$ 5,630,297,000	$ 5,588,430,000		$ 5,688,063,000

[1] Represents the balance at March 31, 2015, and is net of charge-offs of $772,000.

[2] The population of defaulted restructured loans for the period indicated includes only those loans restructured during the preceding 12-month period. The table excludes defaulted troubled restructurings in those classes for which the recorded investment was zero at the end of the period.