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	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	$ 8,204,440	$ 7,119,965
Past Due	49,705	41,750
Total loans	8,254,145	7,161,715
Non-accrual	59,289	29,430
90 Days or More Past Due, Still Accruing Interest	5,009	3,057
Covered loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	22,097	29,808
Past Due	1,177	967
Total loans	23,274	30,775
Non-accrual	479	555
90 Days or More Past Due, Still Accruing Interest	133	174
30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	22,923	19,049
30-89 Days Past Due | Covered loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	918	405
90 Days or More Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	26,782	22,701
90 Days or More Past Due | Covered loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	259	562
Commercial, industrial, and agricultural
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	3,217,154	2,912,166
Commercial, industrial, and agricultural | Commercial and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	2,816,442	2,516,197
Past Due	11,216	8,529
Total loans	2,827,658	2,524,726
Non-accrual	29,938	5,587
90 Days or More Past Due, Still Accruing Interest	374	857
Commercial, industrial, and agricultural | Agricultural
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	388,596	387,109
Past Due	900	331
Total loans	389,496	387,440
Non-accrual	181	355
90 Days or More Past Due, Still Accruing Interest	736	0
Commercial, industrial, and agricultural | 30-89 Days Past Due | Commercial and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	6,426	4,956
Commercial, industrial, and agricultural | 30-89 Days Past Due | Agricultural
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	0	245
Commercial, industrial, and agricultural | 90 Days or More Past Due | Commercial and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	4,790	3,573
Commercial, industrial, and agricultural | 90 Days or More Past Due | Agricultural
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	900	86
Commercial real estate loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	3,601,628	3,051,916
Past Due	25,132	19,934
Total loans	3,626,760	3,071,850
Non-accrual	20,766	14,187
90 Days or More Past Due, Still Accruing Interest	3,259	1,213
Commercial real estate loans | Office, retail, and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	1,563,867	1,386,383
Past Due	17,960	9,071
Total loans	1,581,827	1,395,454
Non-accrual	17,277	6,875
90 Days or More Past Due, Still Accruing Interest	1,129	4
Commercial real estate loans | Multi-family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	612,428	526,625
Past Due	1,606	1,699
Total loans	614,034	528,324
Non-accrual	311	796
90 Days or More Past Due, Still Accruing Interest	604	548
Commercial real estate loans | Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	450,927	216,377
Past Due	613	505
Total loans	451,540	216,882
Non-accrual	286	905
90 Days or More Past Due, Still Accruing Interest	0	0
Commercial real estate loans | Other commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	974,406	922,531
Past Due	4,953	8,659
Total loans	979,359	931,190
Non-accrual	2,892	5,611
90 Days or More Past Due, Still Accruing Interest	1,526	661
Commercial real estate loans | 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	7,824	6,763
Commercial real estate loans | 30-89 Days Past Due | Office, retail, and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	5,327	2,647
Commercial real estate loans | 30-89 Days Past Due | Multi-family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	858	541
Commercial real estate loans | 30-89 Days Past Due | Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	332	0
Commercial real estate loans | 30-89 Days Past Due | Other commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	1,307	3,575
Commercial real estate loans | 90 Days or More Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	17,308	13,171
Commercial real estate loans | 90 Days or More Past Due | Office, retail, and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	12,633	6,424
Commercial real estate loans | 90 Days or More Past Due | Multi-family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	748	1,158
Commercial real estate loans | 90 Days or More Past Due | Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	281	505
Commercial real estate loans | 90 Days or More Past Due | Other commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	3,646	5,084
Total corporate loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	6,806,666	5,955,222
Past Due	37,248	28,794
Total loans	6,843,914	5,984,016
Non-accrual	50,885	20,129
90 Days or More Past Due, Still Accruing Interest	4,369	2,070
Total corporate loans | 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	14,250	11,964
Total corporate loans | 90 Days or More Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	22,998	16,830
Consumer loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	1,375,677	1,134,935
Past Due	11,280	11,989
Total loans	1,386,957	1,146,924
Non-accrual	7,925	8,746
90 Days or More Past Due, Still Accruing Interest	507	813
Consumer loans | Home equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	726,676	647,175
Past Due	5,928	6,293
Total loans	732,604	653,468
Non-accrual	4,986	5,310
90 Days or More Past Due, Still Accruing Interest	17	216
Consumer loans | 1-4 family mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	412,737	350,980
Past Due	3,617	4,874
Total loans	416,354	355,854
Non-accrual	2,939	3,416
90 Days or More Past Due, Still Accruing Interest	231	528
Consumer loans | Installment
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	236,264	136,780
Past Due	1,735	822
Total loans	237,999	137,602
Non-accrual	0	20
90 Days or More Past Due, Still Accruing Interest	259	69
Consumer loans | 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	7,755	6,680
Consumer loans | 30-89 Days Past Due | Home equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	3,627	3,247
Consumer loans | 30-89 Days Past Due | 1-4 family mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	2,652	2,680
Consumer loans | 30-89 Days Past Due | Installment
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	1,476	753
Consumer loans | 90 Days or More Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	3,525	5,309
Consumer loans | 90 Days or More Past Due | Home equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	2,301	3,046
Consumer loans | 90 Days or More Past Due | 1-4 family mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	965	2,194
Consumer loans | 90 Days or More Past Due | Installment
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due	$ 259	$ 69