Past Due Loans, Allowance For Credit Losses, Impaired Loans and TDRS (Details) - Credit Quality Indicators by Class, Excluding Covered Loans - USD ($) $ in Thousands		Jun. 30, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Accruing		$ 2,491	$ 2,743
Special Mention and Substandard Loans
Financing Receivable, Recorded Investment [Line Items]
Accruing		847	862
Commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		2,699,742	2,524,726
Accruing		289	294
Commercial and industrial | Pass
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		2,511,957	2,379,992
Commercial and industrial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[1],[2]	130,476	86,263
Commercial and industrial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[2],[3]	51,006	52,884
Commercial and industrial | Substandard Non-Accrual
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[4]	6,303	5,587
Agricultural
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		401,858	387,440
Agricultural | Pass
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		366,283	381,523
Agricultural | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[1],[2]	17,130	0
Agricultural | Substandard
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[2],[3]	17,970	5,562
Agricultural | Substandard Non-Accrual
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[4]	475	355
Office, retail, and industrial
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		1,529,675	1,395,454
Accruing		159	164
Office, retail, and industrial | Pass
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		1,441,594	1,320,164
Office, retail, and industrial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[1],[2]	38,902	32,627
Office, retail, and industrial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[2],[3]	32,364	35,788
Office, retail, and industrial | Substandard Non-Accrual
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[4]	16,815	6,875
Multi-family
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		587,104	528,324
Accruing		591	598
Multi-family | Pass
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		577,991	517,412
Multi-family | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[1],[2]	4,821	6,146
Multi-family | Substandard
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[2],[3]	3,971	3,970
Multi-family | Substandard Non-Accrual
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[4]	321	796
Construction
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		371,016	216,882
Construction | Pass
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		357,969	201,496
Construction | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[1],[2]	4,250	4,678
Construction | Substandard
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[2],[3]	8,437	9,803
Construction | Substandard Non-Accrual
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[4]	360	905
Other commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		1,000,655	931,190
Accruing		329	340
Other commercial real estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		966,607	898,746
Other commercial real estate | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[1],[2]	12,123	13,179
Other commercial real estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[2],[3]	17,128	13,654
Other commercial real estate | Substandard Non-Accrual
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[4]	4,797	5,611
Total commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		3,488,450	3,071,850
Accruing		1,079	1,102
Total commercial real estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		3,344,161	2,937,818
Total commercial real estate | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[1],[2]	60,096	56,630
Total commercial real estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[2],[3]	61,900	63,215
Total commercial real estate | Substandard Non-Accrual
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[4]	22,293	14,187
Total corporate loans
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		6,590,050	5,984,016
Accruing		1,368	1,396
Total corporate loans | Pass
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		6,222,401	5,699,333
Total corporate loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[1],[2]	207,702	142,893
Total corporate loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[2],[3]	130,876	121,661
Total corporate loans | Substandard Non-Accrual
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[4]	$ 29,071	$ 20,129

[1] Loans categorized as special mention exhibit potential weaknesses that require the close attention of management since these potential weaknesses may result in the deterioration of repayment prospects in the future.

[2] Total special mention and substandard loans includes accruing TDRs of $847,000 as of June 30, 2016 and $862,000 as of December 31, 2015.

[3] Loans categorized as substandard exhibit well-defined weaknesses that may jeopardize the liquidation of the debt. These loans continue to accrue interest because they are well secured and collection of principal and interest is expected within a reasonable time.

[4] Loans categorized as non-accrual exhibit well-defined weaknesses that may jeopardize the liquidation of the debt or result in a loss if the deficiencies are not corrected.