Loans (Schedule of Consumer Loans LTV Distributions) (Details) - USD ($)	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 38,530,400,000	$ 30,998,900,000	$ 31,247,000,000.0
PCI Loans
Financing Receivable, Recorded Investment [Line Items]
Loans		1,277,600,000
Covered Loans
Financing Receivable, Recorded Investment [Line Items]
Loans	0
Consumer Loans
Financing Receivable, Recorded Investment [Line Items]
2020	354,300,000
2019	1,756,000,000.0
2018	931,400,000
2017	904,900,000
2016	520,300,000
2015 & Prior	3,224,300,000
Revolving Loans Amortized Cost Basis	67,100,000
Revolving Loans Converted to Term Loans Amortized Cost Basis	75,300,000
Loans	7,833,600,000	5,979,400,000
Consumer Loans | Covered Loans
Financing Receivable, Recorded Investment [Line Items]
Loans		307,800,000
Consumer Loans | Covered Loans | PCI Loans
Financing Receivable, Recorded Investment [Line Items]
Loans		293,700,000
Consumer Loans | Non-covered Loans
Financing Receivable, Recorded Investment [Line Items]
Loans		4,421,800,000
Consumer Loans | Non-covered Loans | PCI Loans
Financing Receivable, Recorded Investment [Line Items]
Loans		956,100,000
Consumer Loans | LTV Greater Than 125 Percent
Financing Receivable, Recorded Investment [Line Items]
Loans		61,200,000
Consumer Loans | LTV Greater Than 125 Percent | Covered Loans | PCI Loans
Financing Receivable, Recorded Investment [Line Items]
Loans		2,800,000
Consumer Loans | LTV Greater Than 125 Percent | Non-covered Loans
Financing Receivable, Recorded Investment [Line Items]
Loans		5,200,000
Consumer Loans | LTV Greater Than 125 Percent | Non-covered Loans | PCI Loans
Financing Receivable, Recorded Investment [Line Items]
Loans		53,200,000
Consumer Loans | LTV 101% – 125%
Financing Receivable, Recorded Investment [Line Items]
Loans		108,100,000
Consumer Loans | LTV 101% – 125% | Covered Loans | PCI Loans
Financing Receivable, Recorded Investment [Line Items]
Loans		8,500,000
Consumer Loans | LTV 101% – 125% | Non-covered Loans
Financing Receivable, Recorded Investment [Line Items]
Loans		6,600,000
Consumer Loans | LTV 101% – 125% | Non-covered Loans | PCI Loans
Financing Receivable, Recorded Investment [Line Items]
Loans		93,000,000.0
Consumer Loans | LTV 80% – 100%
Financing Receivable, Recorded Investment [Line Items]
Loans		471,100,000
Consumer Loans | LTV 80% – 100% | Covered Loans
Financing Receivable, Recorded Investment [Line Items]
Loans		300,000
Consumer Loans | LTV 80% – 100% | Covered Loans | PCI Loans
Financing Receivable, Recorded Investment [Line Items]
Loans		48,100,000
Consumer Loans | LTV 80% – 100% | Non-covered Loans
Financing Receivable, Recorded Investment [Line Items]
Loans		183,400,000
Consumer Loans | LTV 80% – 100% | Non-covered Loans | PCI Loans
Financing Receivable, Recorded Investment [Line Items]
Loans		239,300,000
Consumer Loans | LTV Less than 80%
Financing Receivable, Recorded Investment [Line Items]
Loans		5,337,900,000
Consumer Loans | LTV Less than 80% | Covered Loans
Financing Receivable, Recorded Investment [Line Items]
Loans		307,500,000
Consumer Loans | LTV Less than 80% | Covered Loans | PCI Loans
Financing Receivable, Recorded Investment [Line Items]
Loans		234,300,000
Consumer Loans | LTV Less than 80% | Non-covered Loans
Financing Receivable, Recorded Investment [Line Items]
Loans		4,225,500,000
Consumer Loans | LTV Less than 80% | Non-covered Loans | PCI Loans
Financing Receivable, Recorded Investment [Line Items]
Loans		570,600,000
Consumer Loans | Loan To Value Not Available
Financing Receivable, Recorded Investment [Line Items]
Loans		1,100,000
Consumer Loans | Loan To Value Not Available | Non-covered Loans
Financing Receivable, Recorded Investment [Line Items]
Loans		1,100,000
Consumer Loans | Consumer and Community Banking
Financing Receivable, Recorded Investment [Line Items]
Loans		$ 4,524,000,000.0
Consumer Loans | Consumer Banking | Legacy Consumer Mortgages
Financing Receivable, Recorded Investment [Line Items]
2015 & Prior	2,036,100,000
Revolving Loans Converted to Term Loans Amortized Cost Basis	56,300,000
Loans	2,092,400,000
Consumer Loans | Consumer Banking | Legacy Consumer Mortgages | Junior Lien Loans
Financing Receivable, Recorded Investment [Line Items]
2015 & Prior	3,800,000
Revolving Loans Converted to Term Loans Amortized Cost Basis	23,200,000
Loans	27,000,000.0
Consumer Loans | Consumer Banking | Legacy Consumer Mortgages | Loans Insured or Guaranteed by US Government Authorities
Financing Receivable, Recorded Investment [Line Items]
2015 & Prior	23,800,000
Loans	23,800,000
Consumer Loans | Consumer Banking | Legacy Consumer Mortgages | LTV Greater Than 125 Percent
Financing Receivable, Recorded Investment [Line Items]
2015 & Prior	57,400,000
Revolving Loans Converted to Term Loans Amortized Cost Basis	400,000
Loans	57,800,000
Consumer Loans | Consumer Banking | Legacy Consumer Mortgages | LTV 101% – 125%
Financing Receivable, Recorded Investment [Line Items]
2015 & Prior	94,300,000
Revolving Loans Converted to Term Loans Amortized Cost Basis	1,100,000
Loans	95,400,000
Consumer Loans | Consumer Banking | Legacy Consumer Mortgages | LTV 80% – 100%
Financing Receivable, Recorded Investment [Line Items]
2015 & Prior	303,400,000
Revolving Loans Converted to Term Loans Amortized Cost Basis	4,700,000
Loans	308,100,000
Consumer Loans | Consumer Banking | Legacy Consumer Mortgages | LTV Less than 80%
Financing Receivable, Recorded Investment [Line Items]
2015 & Prior	1,553,400,000
Revolving Loans Converted to Term Loans Amortized Cost Basis	26,900,000
Loans	1,580,300,000
Consumer Loans | Consumer Banking | Consumer and Community Banking
Financing Receivable, Recorded Investment [Line Items]
2020	354,300,000
2019	1,756,000,000.0
2018	931,400,000
2017	904,900,000
2016	520,300,000
2015 & Prior	1,188,200,000
Revolving Loans Amortized Cost Basis	67,100,000
Revolving Loans Converted to Term Loans Amortized Cost Basis	19,000,000.0
Loans	5,741,200,000
Consumer Loans | Consumer Banking | Consumer and Community Banking | Junior Lien Loans
Financing Receivable, Recorded Investment [Line Items]
2020	100,000
2019	100,000
2018	100,000
2017	400,000
2016	200,000
2015 & Prior	5,800,000
Revolving Loans Amortized Cost Basis	44,300,000
Revolving Loans Converted to Term Loans Amortized Cost Basis	9,800,000
Loans	60,800,000
Consumer Loans | Consumer Banking | Consumer and Community Banking | Loans Insured or Guaranteed by US Government Authorities
Financing Receivable, Recorded Investment [Line Items]
2020	800,000
2019	50,100,000
2018	23,000,000.0
2017	92,800,000
2016	11,100,000
2015 & Prior	8,400,000
Loans	186,200,000
Consumer Loans | Consumer Banking | Consumer and Community Banking | LTV Greater Than 125 Percent
Financing Receivable, Recorded Investment [Line Items]
Revolving Loans Amortized Cost Basis	400,000
Loans	400,000
Consumer Loans | Consumer Banking | Consumer and Community Banking | LTV 80% – 100%
Financing Receivable, Recorded Investment [Line Items]
2020	15,200,000
2019	68,500,000
2018	26,500,000
2017	3,300,000
2016	300,000
2015 & Prior	1,700,000
Revolving Loans Amortized Cost Basis	3,000,000.0
Loans	118,500,000
Consumer Loans | Consumer Banking | Consumer and Community Banking | LTV Less than 80%
Financing Receivable, Recorded Investment [Line Items]
2020	338,200,000
2019	1,636,000,000.0
2018	880,700,000
2017	807,900,000
2016	507,800,000
2015 & Prior	1,156,900,000
Revolving Loans Amortized Cost Basis	15,300,000
Revolving Loans Converted to Term Loans Amortized Cost Basis	9,200,000
Loans	5,352,000,000.0
Consumer Loans | Consumer Banking | Consumer and Community Banking | No LTV required
Financing Receivable, Recorded Investment [Line Items]
2019	1,300,000
2018	1,100,000
2017	500,000
2016	900,000
2015 & Prior	15,400,000
Revolving Loans Amortized Cost Basis	4,100,000
Loans	$ 23,300,000