Investments (Narrative) (Details) shares in Thousands			12 Months Ended
		May 01, 2018 USD ($)	Dec. 31, 2018 USD ($) investment investments shares	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jan. 01, 2018 USD ($)
Schedule of Investments [Line Items]
Investment in marketable equity securities			$ 92,599,000	$ 0
Cumulative effect of new accounting principle in period of adoption						$ (50,051,000)
Investment securities available for sale transferred to held to maturity fair value, net of tax		$ 109,500,000	(109,507,000)	0	$ 0
Other Comprehensive Income Loss Unrealized Losses On Securities Available For Sale Transferred To Held To Maturity Arising During Period Net Of Tax		84,000,000	(71,149,000)	0	0
Other Comprehensive Income Loss Reclassification Adjustment For Accretion On Unrealized Losses On Securities Available For Sale Transferred To Held To Maturity Arising During Period Before Tax			(17,106,000)	0	$ 0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]		$ (23,667,000)	(3,419,000)
Number of investments in continuous unrealized loss position for more than twelve months | investment			221
Held-to-maturity, securities in unrealized loss positions, qualitative disclosure, number of positions | investment			2
Unrealized losses related to marketability of securities or issuers ability to honor redemption obligations			$ 0
Investment value deemed to be OTTI			0
Investment securities, aggregate carrying value, pledged as collateral			$ 4,030,826,000	4,593,198,000
Visa Class B Common Stock
Schedule of Investments [Line Items]
Investment owned (in shares) | shares			298
Investment owned, fair value			$ 0
Equity Securities
Schedule of Investments [Line Items]
Fair value of marketable equity securities				$ 105,208,000
Mortgage Backed Securities
Schedule of Investments [Line Items]
Investment securities available for sale transferred to held to maturity amortized cost		2,490,000,000
Investment securities available for sale transferred to held to maturity fair value		$ 2,380,000,000
Number of investments in continuous unrealized loss position for more than twelve months | investments			213
U. S. Treasury
Schedule of Investments [Line Items]
Number of investments in continuous unrealized loss position for more than twelve months | investments			7
Corporate Bonds
Schedule of Investments [Line Items]
Available-for-sale, securities in unrealized loss positions, number of positions, greater than or equal to on year | investments			1
Financial Instruments ASU cumulative effect adjustment
Schedule of Investments [Line Items]
Cumulative effect of new accounting principle in period of adoption						$ 18,700,000

[1] Amounts in parentheses indicate debits to profit/loss.