Past Due Loans, Allowance For Credit Losses, Impaired Loans and TDRS (Details) - Aging Analysis of Past Due Loans and Non-Performing Loans by Class (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	$ 6,436,799	$ 5,598,612
30-89 Days Past Due	20,002	24,770
90 Days or More Past Due	62,278	90,978
Total Past Due	82,280	115,748
Total Loans	6,519,079	5,714,360
Non- accrual Loans	75,433	80,740
90 Days Past Due Loans, Still Accruing Interest	13,093	21,789
Commercial And Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	2,197,785	1,814,660
30-89 Days Past Due	6,216	6,872
90 Days or More Past Due	4,165	9,106
Total Past Due	10,381	15,978
Total Loans	2,208,166	1,830,638
Non- accrual Loans	19,696	11,767
90 Days Past Due Loans, Still Accruing Interest	1,256	393
Agricultural
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	347,179	321,156
30-89 Days Past Due	0	134
90 Days or More Past Due	332	412
Total Past Due	332	546
Total Loans	347,511	321,702
Non- accrual Loans	361	519
90 Days Past Due Loans, Still Accruing Interest	0	0
Office Retail And Industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	1,401,990	1,335,027
30-89 Days Past Due	1,842	2,620
90 Days or More Past Due	18,690	16,038
Total Past Due	20,532	18,658
Total Loans	1,422,522	1,353,685
Non- accrual Loans	16,963	17,076
90 Days Past Due Loans, Still Accruing Interest	3,840	1,315
Multi-Family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	557,852	330,960
30-89 Days Past Due	641	318
90 Days or More Past Due	1,196	1,595
Total Past Due	1,837	1,913
Total Loans	559,689	332,873
Non- accrual Loans	1,536	1,848
90 Days Past Due Loans, Still Accruing Interest	0	0
Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	186,363	180,083
30-89 Days Past Due	0	23
90 Days or More Past Due	7,082	6,091
Total Past Due	7,082	6,114
Total Loans	193,445	186,197
Non- accrual Loans	7,082	6,297
90 Days Past Due Loans, Still Accruing Interest	0	0
Other Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	861,061	795,462
30-89 Days Past Due	4,461	5,365
90 Days or More Past Due	6,303	6,244
Total Past Due	10,764	11,609
Total Loans	871,825	807,071
Non- accrual Loans	7,912	8,153
90 Days Past Due Loans, Still Accruing Interest	150	258
Total Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	3,007,266	2,641,532
30-89 Days Past Due	6,944	8,326
90 Days or More Past Due	33,271	29,968
Total Past Due	40,215	38,294
Total Loans	3,047,481	2,679,826
Non- accrual Loans	33,493	33,374
90 Days Past Due Loans, Still Accruing Interest	3,990	1,573
Total Corporate Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	5,552,230	4,777,348
30-89 Days Past Due	13,160	15,332
90 Days or More Past Due	37,768	39,486
Total Past Due	50,928	54,818
Total Loans	5,603,158	4,832,166
Non- accrual Loans	53,550	45,660
90 Days Past Due Loans, Still Accruing Interest	5,246	1,966
Home Equity Line of Credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	509,530	415,791
30-89 Days Past Due	3,525	4,830
90 Days or More Past Due	4,391	6,399
Total Past Due	7,916	11,229
Total Loans	517,446	427,020
Non- accrual Loans	5,834	6,864
90 Days Past Due Loans, Still Accruing Interest	587	1,102
1-4 family mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	234,672	268,912
30-89 Days Past Due	1,935	2,046
90 Days or More Past Due	1,565	5,034
Total Past Due	3,500	7,080
Total Loans	238,172	275,992
Non- accrual Loans	3,235	5,198
90 Days Past Due Loans, Still Accruing Interest	126	548
Installment Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	66,997	42,350
30-89 Days Past Due	428	330
90 Days or More Past Due	2,003	2,147
Total Past Due	2,431	2,477
Total Loans	69,428	44,827
Non- accrual Loans	1,909	2,076
90 Days Past Due Loans, Still Accruing Interest	103	92
Total Consumer Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	811,199	727,053
30-89 Days Past Due	5,888	7,206
90 Days or More Past Due	7,959	13,580
Total Past Due	13,847	20,786
Total Loans	825,046	747,839
Non- accrual Loans	10,978	14,138
90 Days Past Due Loans, Still Accruing Interest	816	1,742
Total Loans Excluding Covered Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	6,363,429	5,504,401
30-89 Days Past Due	19,048	22,538
90 Days or More Past Due	45,727	53,066
Total Past Due	64,775	75,604
Total Loans	6,428,204	5,580,005
Non- accrual Loans	64,528	59,798
90 Days Past Due Loans, Still Accruing Interest	6,062	3,708
Covered Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	73,370	94,211
30-89 Days Past Due	954	2,232
90 Days or More Past Due	16,551	37,912
Total Past Due	17,505	40,144
Total Loans	90,875	134,355
Non- accrual Loans	10,905	20,942
90 Days Past Due Loans, Still Accruing Interest	$ 7,031	$ 18,081