Past Due Loans, Allowance For Credit Losses, Impaired Loans, and TDRS (Details) - Credit Quality Indicators by Class - USD ($) $ in Thousands		Jun. 30, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Accruing		$ 2,029	$ 2,291
Special Mention and Substandard Loans
Financing Receivable, Recorded Investment [Line Items]
Accruing		669	834
Total corporate loans
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		8,436,835	6,843,914
Total corporate loans | Pass
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		8,040,671	6,493,630
Total corporate loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[1],[2]	144,537	159,675
Total corporate loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[2],[3]	180,718	139,724
Total corporate loans | Non-accrual
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[4]	70,909	50,885
Commercial, industrial, and agricultural | Commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		3,410,748	2,827,658
Accruing		273	281
Commercial, industrial, and agricultural | Commercial and industrial | Pass
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		3,199,001	2,638,833
Commercial, industrial, and agricultural | Commercial and industrial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[1],[2]	67,252	92,340
Commercial, industrial, and agricultural | Commercial and industrial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[2],[3]	93,095	66,547
Commercial, industrial, and agricultural | Commercial and industrial | Non-accrual
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[4]	51,400	29,938
Commercial, industrial, and agricultural | Agricultural
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		433,424	389,496
Accruing		0	0
Commercial, industrial, and agricultural | Agricultural | Pass
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		409,969	366,382
Commercial, industrial, and agricultural | Agricultural | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[1],[2]	14,464	17,039
Commercial, industrial, and agricultural | Agricultural | Substandard
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[2],[3]	8,604	5,894
Commercial, industrial, and agricultural | Agricultural | Non-accrual
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[4]	387	181
Commercial real estate loans
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		4,592,663	3,626,760
Accruing		776	1,009
Commercial real estate loans | Pass
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		4,431,701	3,488,415
Commercial real estate loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[1],[2]	62,821	50,296
Commercial real estate loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[2],[3]	79,019	67,283
Commercial real estate loans | Non-accrual
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[4]	19,122	20,766
Commercial real estate loans | Office, retail, and industrial
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		1,983,802	1,581,827
Accruing		0	155
Commercial real estate loans | Office, retail, and industrial | Pass
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		1,896,327	1,491,030
Commercial real estate loans | Office, retail, and industrial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[1],[2]	27,894	34,007
Commercial real estate loans | Office, retail, and industrial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[2],[3]	44,550	39,513
Commercial real estate loans | Office, retail, and industrial | Non-accrual
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[4]	15,031	17,277
Commercial real estate loans | Multi-family
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		681,032	614,034
Accruing		579	586
Commercial real estate loans | Multi-family | Pass
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		673,946	607,324
Commercial real estate loans | Multi-family | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[1],[2]	5,051	4,370
Commercial real estate loans | Multi-family | Substandard
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[2],[3]	1,877	2,029
Commercial real estate loans | Multi-family | Non-accrual
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[4]	158	311
Commercial real estate loans | Construction
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		543,892	451,540
Accruing		0	0
Commercial real estate loans | Construction | Pass
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		523,046	438,946
Commercial real estate loans | Construction | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[1],[2]	8,739	111
Commercial real estate loans | Construction | Substandard
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[2],[3]	11,910	12,197
Commercial real estate loans | Construction | Non-accrual
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[4]	197	286
Commercial real estate loans | Other commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		1,383,937	979,359
Accruing		197	268
Commercial real estate loans | Other commercial real estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class		1,338,382	951,115
Commercial real estate loans | Other commercial real estate | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[1],[2]	21,137	11,808
Commercial real estate loans | Other commercial real estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[2],[3]	20,682	13,544
Commercial real estate loans | Other commercial real estate | Non-accrual
Financing Receivable, Recorded Investment [Line Items]
Credit Quality Indicators by Class	[4]	$ 3,736	$ 2,892

[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 $669,000 as of June 30, 2017 and $834,000 as of December 31, 2016.

[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.