Fair Value Measurements, Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands		Sep. 30, 2019	Dec. 31, 2018
Financial assets
Cash and due from banks		$ 523,435	$ 507,187
Interest-bearing deposits in other financial institutions		236,010	221,226
Federal funds sold and securities purchased under agreements to resell		100	148,285
Investment securities held to maturity	[1]	2,200,419	2,740,511
Investment securities held to maturity, fair value		2,281,285	2,710,271
Investment securities available for sale	[1]	3,436,289	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
Investment securities gains (losses), net		15,096	1,568
FHLB and Federal Reserve Bank stocks		207,443	250,534
Loans, net		22,540,285	22,702,406
Financial liabilities
Short-term funding		108,444	157,074
Other long-term funding		796,799	795,611
FHLB advances		2,877,727	3,574,371
Letters of Credit Outstanding, Amount		272,000	256,000
Fair Value, Inputs, Level 1
Financial assets
Cash and due from banks		523,435	507,187
Cash and due from banks, Fair Value		523,435	507,187
Interest-bearing deposits in other financial institutions		236,010	221,226
Interest-bearing deposits in other financial institutions, fair value		236,010	221,226
Federal funds sold and securities purchased under agreements to resell		100	148,285
Federal funds sold and securities purchased under agreements to resell, fair value		100	148,285
Investment 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		1,652	1,568
Equity securities with readily determinable fair values, Fair Value		1,652	1,568
Fair Value, Inputs, Level 2
Financial assets
Investment securities held to maturity		2,199,420	2,740,511
Investment securities held to maturity, fair value		2,280,265	2,710,271
Investment securities available for sale		3,436,289	3,945,943
Investment securities available for sale, fair value		3,436,289	3,945,943
FHLB and Federal Reserve Bank stocks		207,443	250,534
FHLB and Federal Reserve Bank stocks, fair value		207,443	250,534
Residential Loans Receivable Held-for-sale, Net, Not Part of Disposal Group		137,655	64,321
Residential Held-for-sale, Fair Value Disclosure		137,655	64,321
Commercial loans held for sale		11,597	14,943
Commercial Loans Held-for-sale, Fair Value Disclosure		11,597	14,943
Bank and Corporate Owned Life Insurance		670,739	663,203
Bank owned life insurance, fair value		670,739	663,203
Financial liabilities
Brokered CDs and other time deposits		2,909,759	2,815,401
Brokered CDs and other time deposits, fair value		2,910,112	2,815,401
Short-term funding		108,444	157,074
Short-term funding, fair value		108,444	157,074
Other long-term funding		796,799	795,611
Long-term funding, fair value		842,196	826,612
FHLB advances		2,877,727	3,574,371
Advances, Fair Value Disclosure		2,938,923	3,565,572
Standby letters of credit		2,715	2,482
Standby letters of credit, fair value		2,715	2,482
Fair Value, Inputs, Level 2 | Other Assets [Member]
Financial assets
Derivative Asset		129,044	89,052
Derivatives (trading and other assets), fair value		129,044	89,052
Fair Value, Inputs, Level 2 | Other Liabilities [Member]
Financial liabilities
Derivatives (trading liabilities)		45,180	87,817
Derivatives (trading and other liabilities), fair value		45,180	87,817
Fair Value, Inputs, Level 3
Financial assets
Equity Securities without Readily Determinable Fair Value, Amount		13,444	0
Investment securities gains (losses), net		13,444	0
Loans, net		22,540,285	22,702,406
Loans, net, fair value		22,422,568	22,317,395
Derivative Asset		2,017	2,208
Derivatives (trading and other assets), fair value		2,017	2,208
Financial liabilities
Noninterest-bearing demand, savings, interest-bearing demand, and money market accounts		21,512,804	22,081,992
Noninterest-bearing demand, savings, interest-bearing demand, and money market deposits, fair value		21,512,804	22,081,992
Derivatives (trading liabilities)		590	2,072
Derivatives (trading and other liabilities), fair value		$ 590	$ 2,072

[1] (a) As permitted by ASU 2019-04, which was adopted during the third quarter of 2019, the Corporation made a one-time election to transfer municipal securities with a book value of $692 million from held to maturity to available for sale.