Loans and Credit Quality (Details 1) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance	$ 99,375		$ 99,375			$ 84,455
Allowance for loan and lease losses	99,375	$ 82,149	99,375	$ 82,149	$ 92,378	84,455	$ 81,180	$ 82,034
Allowance for Loan and Lease Losses, Write-offs	(623)	(5,434)	(11,113)	(6,933)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	2,091	1,242	4,633	1,931
Provision for Loan and Lease Losses	5,529	5,161	21,400	5,117
Loans and Leases Receivable, Net of Deferred Income	12,034,189		12,034,189			11,882,432
Loans and Leases Receivable Net Of Deferred Income Covered And Noncovered	12,034,189	11,190,105	12,034,189	11,190,105
Mortgage Loans on Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance	29,908	22,276	29,908	22,276
Real Estate Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance	3,908	4,302	3,908	4,302
Commercial Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance	50,531	35,530	50,531	35,530
Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance	700	3,415	700	3,415
Purchased Credit Impaired Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance	14,328		14,328			13,999
Loans and Leases Receivable, Allowance, Covered	14,328	16,626	14,328	16,626	12,698	13,999	21,200	21,793
Allowance for Loan and Lease Losses, Write-offs	0	(4,604)	(579)	(4,553)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	101	0	112	0
Provision for Loan and Lease Losses	1,529	30	796	(614)
Financing Receivable, Allowance for Credit Losses, Acquired with Deteriorated Credit Quality	14,328	16,626	14,328	16,626
Receivables Acquired with Deteriorated Credit Quality	222,638	398,436	222,638	398,436
Loans and Leases Receivable, Net of Deferred Income	222,638	398,436	222,638	398,436		290,791
NonCovered [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance	85,047	65,523	85,047	65,523	79,680	70,456	59,980	60,241
Impaired Financing Receivable, Related Allowance	15,008		15,008			10,774
Allowance for Loan and Lease Losses, Write-offs	(623)	(830)	(10,534)	(2,380)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	1,990	1,242	4,521	1,931
Provision for Loan and Lease Losses	4,000	5,131	20,604	5,731
Financing Receivable, Individually Evaluated for Impairment	15,008	15,335	15,008	15,335
Financing Receivable, Collectively Evaluated for Impairment	70,039	50,188	70,039	50,188
Financing Receivable, Individually Evaluated for Impairment	166,767	130,543	166,767	130,543
Financing Receivable, Collectively Evaluated for Impairment	11,644,784	10,661,126	11,644,784	10,661,126
Loans and Leases Receivable, Net of Deferred Income	11,811,551	10,791,669	11,811,551	10,791,669		11,591,641
NonCovered [Member] | Mortgage Loans on Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance					30,911	25,097	24,352	26,078
Impaired Financing Receivable, Related Allowance	1,461		1,461			693
Allowance for Loan and Lease Losses, Write-offs	(62)	(487)	(1,515)	(581)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	200	376	1,495	636
Provision for Loan and Lease Losses	(1,141)	(1,965)	4,831	(3,857)
Financing Receivable, Individually Evaluated for Impairment	1,461	2,245	1,461	2,245
Financing Receivable, Collectively Evaluated for Impairment	28,447	20,031	28,447	20,031
Financing Receivable, Individually Evaluated for Impairment	56,297	62,287	56,297	62,287
Financing Receivable, Collectively Evaluated for Impairment	5,359,373	5,174,165	5,359,373	5,174,165
Loans and Leases Receivable, Net of Deferred Income	5,415,670	5,236,452	5,415,670	5,236,452		5,340,560
NonCovered [Member] | Real Estate Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance					2,173	4,248	4,103	4,298
Impaired Financing Receivable, Related Allowance	49		49			69
Allowance for Loan and Lease Losses, Write-offs	0	0	0	0
Allowance for Loan and Lease Loss, Recovery of Bad Debts	12	64	644	88
Provision for Loan and Lease Losses	1,723	135	(984)	(84)
Financing Receivable, Individually Evaluated for Impairment	49	238	49	238
Financing Receivable, Collectively Evaluated for Impairment	3,859	4,064	3,859	4,064
Financing Receivable, Individually Evaluated for Impairment	8,118	12,797	8,118	12,797
Financing Receivable, Collectively Evaluated for Impairment	335,382	285,680	335,382	285,680
Loans and Leases Receivable, Net of Deferred Income	343,500	298,477	343,500	298,477		307,135
NonCovered [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance					45,794	39,858	27,740	26,921
Impaired Financing Receivable, Related Allowance	13,305		13,305			9,975
Allowance for Loan and Lease Losses, Write-offs	(534)	(326)	(8,929)	(1,767)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	1,744	587	2,154	965
Provision for Loan and Lease Losses	3,527	7,529	17,448	9,411
Financing Receivable, Individually Evaluated for Impairment	13,305	12,531	13,305	12,531
Financing Receivable, Collectively Evaluated for Impairment	37,226	22,999	37,226	22,999
Financing Receivable, Individually Evaluated for Impairment	98,767	51,488	98,767	51,488
Financing Receivable, Collectively Evaluated for Impairment	5,867,335	5,142,247	5,867,335	5,142,247
Loans and Leases Receivable, Net of Deferred Income	5,966,102	5,193,735	5,966,102	5,193,735		5,842,463
NonCovered [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance					$ 802	1,253	$ 3,785	$ 2,944
Impaired Financing Receivable, Related Allowance	193		193			37
Allowance for Loan and Lease Losses, Write-offs	(27)	(17)	(90)	(32)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	34	215	228	242
Provision for Loan and Lease Losses	(109)	(568)	(691)	261
Financing Receivable, Individually Evaluated for Impairment	193	321	193	321
Financing Receivable, Collectively Evaluated for Impairment	507	3,094	507	3,094
Financing Receivable, Individually Evaluated for Impairment	3,585	3,971	3,585	3,971
Financing Receivable, Collectively Evaluated for Impairment	82,694	59,034	82,694	59,034
Loans and Leases Receivable, Net of Deferred Income	$ 86,279	$ 63,005	$ 86,279	$ 63,005		$ 101,483