Goodwill Mortgage Servicing Rights (Commercial and Residential Mortgage Loan Servicing Assets - Key Valuation Assumptions) (Details) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Fair Value	$ 1,627,000	$ 1,983,000
Mortgage Servicing Rights [Member] | Commercial Mortgage [Member]
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Fair Value	$ 630,000	$ 726,000	$ 748,000	$ 668,000
Weighted-average life (years)	4 years	4 years 1 month 6 days
Decline in fair value from 10% adverse change in prepayment rate	$ 9,000	$ 10,000
Decline in fair value from 20% adverse change in prepayment rate	17,000	19,000
Decline in fair value from 10% adverse change in interest rate	16,000	19,000
Decline in fair value from 20% adverse change in interest rate	31,000	39,000
Mortgage Servicing Rights [Member] | Residential Mortgage [Member]
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Fair Value	$ 997,000	$ 1,257,000	$ 1,297,000	$ 1,164,000
Weighted-average life (years)	5 years 2 months 12 days	6 years 10 months 24 days
Decline in fair value from 10% adverse change in prepayment rate	$ 47,000	$ 41,000
Decline in fair value from 20% adverse change in prepayment rate	$ 89,000	$ 79,000
Spread over the benchmark curve	7.86%	8.06%
Decline in fair value from 10% adverse change in adjusted spread	$ 27,000	$ 37,000
Decline in fair value from 20% adverse change in adjusted spread	$ 52,000	$ 73,000
Mortgage Servicing Rights [Member] | Measurement Input, Constant Prepayment Rate [Member] | Commercial Mortgage [Member]
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Servicing asset, measurement input	0.0491	0.0565
Mortgage Servicing Rights [Member] | Measurement Input, Constant Prepayment Rate [Member] | Residential Mortgage [Member]
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Servicing asset, measurement input	0.1356	0.0869
Mortgage Servicing Rights [Member] | Measurement Input, Discount Rate [Member] | Commercial Mortgage [Member]
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Servicing asset, measurement input	0.0788	0.0839