Fair Value Measurements, Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands		6 Months Ended
		Jun. 30, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Visa Restricted Stock Owned		77,000
Financial assets
Cash and due from banks		$ 382,985	$ 507,187
Interest-bearing deposits in other financial institutions		172,708	221,226
Federal funds sold and securities purchased under agreements to resell		1,385	148,285
Debt Securities, Held-to-maturity		2,806,064	2,740,511
Investment securities held to maturity, fair value		2,874,758	2,710,271
Investment securities available for sale		3,283,456	3,946,941
Equity securities with readily determinable fair values, Fair Value		2,000	2,000
Equity Securities without Readily Determinable Fair Value, Amount		13,000	0
Equity Securities, FV-NI and without Readily Determinable Fair Value		15,066	1,568
FHLB and Federal Reserve Bank stocks		202,758	250,534
Loans, net		23,016,308	22,702,406
Financial liabilities
Short-term funding		111,983	157,074
Other long-term funding		796,403	795,611
FHLB advances		2,742,941	3,574,371
Letters of Credit Outstanding, Amount		265,000	256,000
Fair Value, Inputs, Level 1
Financial assets
Cash and due from banks		382,985	507,187
Cash and due from banks, Fair Value		382,985	507,187
Interest-bearing deposits in other financial institutions		172,708	221,226
Interest-bearing deposits in other financial institutions, fair value		172,708	221,226
Federal funds sold and securities purchased under agreements to resell		1,385	148,285
Federal funds sold and securities purchased under agreements to resell, fair value		1,385	148,285
Debt Securities, Held-to-maturity		999	0
Investment securities held to maturity, fair value		1,019	0
Investment securities available for sale		0	999
Investment securities available for sale, fair value		0	999
Equity securities with readily determinable fair value, Carrying Amount		1,621	1,568
Equity securities with readily determinable fair values, Fair Value		1,621	1,568
Fair Value, Inputs, Level 2
Financial assets
Debt Securities, Held-to-maturity		2,805,066	2,740,511
Investment securities held to maturity, fair value		2,873,739	2,710,271
Investment securities available for sale		3,283,456	3,945,943
Investment securities available for sale, fair value		3,283,456	3,945,943
FHLB and Federal Reserve Bank stocks		202,758	250,534
FHLB and Federal Reserve Bank stocks, fair value		202,758	250,534
Residential Loans Receivable Held-for-sale, Net, Not Part of Disposal Group		129,303	64,321
Residential Held-for-sale, Fair Value Disclosure		129,303	64,321
Commercial loans held for sale		11,000	14,943
Commercial Loans Held-for-sale, Fair Value Disclosure		11,000	14,943
Bank and Corporate Owned Life Insurance		668,638	663,203
Bank owned life insurance, fair value		668,638	663,203
Financial liabilities
Brokered CDs and other time deposits	[1]	3,367,252	2,815,401
Brokered CDs and other time deposits, fair value	[1]	3,373,332	2,815,401
Short-term funding	[2]	111,983	157,074
Short-term funding, fair value	[2]	111,983	157,074
Other long-term funding		796,403	795,611
Long-term funding, fair value		840,323	826,612
FHLB advances		2,742,941	3,574,371
Advances, Fair Value Disclosure		2,781,103	3,565,572
Standby letters of credit	[3]	2,693	2,482
Standby letters of credit, fair value	[3]	2,693	2,482
Fair Value, Inputs, Level 3
Financial assets
Equity Securities without Readily Determinable Fair Value, Amount		13,444	0
Equity Securities, FV-NI and without Readily Determinable Fair Value		13,444	0
Loans, net		23,016,308	22,702,406
Loans, net, fair value		22,767,412	22,317,395
Derivatives (trading assets)		4,869	2,208
Derivatives (trading and other assets), fair value		4,869	2,208
Financial liabilities
Noninterest-bearing demand, savings, interest-bearing demand, and money market accounts		21,906,970	22,081,992
Noninterest-bearing demand, savings, interest-bearing demand, and money market deposits, fair value		21,906,970	22,081,992
Derivatives (trading liabilities)		1,903	2,072
Derivatives (trading and other liabilities), fair value		1,903	2,072
Other Assets [Member] | Fair Value, Inputs, Level 2
Financial assets
Derivatives (trading assets)		102,641	89,052
Derivatives (trading and other assets), fair value		102,641	89,052
Other Liabilities [Member] | Fair Value, Inputs, Level 2
Financial liabilities
Derivatives (trading liabilities)		39,641	87,817
Derivatives (trading and other liabilities), fair value		$ 39,641	$ 87,817

[1]
(a) When the estimated fair value is less than the carrying value, the carrying value is reported as the fair value.

[2] (b) The carrying amount is a reasonable estimate of fair value for existing short-term funding.

[3] (b) The carrying amount is a reasonable estimate of fair value for existing short-term funding. (c) The commitment on standby letters of credit was $265 million at June 30, 2019 and $256 million at December 31, 2018. See Note 12 for additional information on the standby letters of credit and for information on the fair value of lending-related commitments.