Mortgage Servicing Assets - Schedule of Range and Weighted-Average of Significant Unobservable Inputs (Details) - Discounted Cash Flow [Member] - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Commercial Mortgage Backed Securities [Member] | Minimum [Member]
Servicing Assets at Fair Value [Line Items]
Expected defaults	1.00%	1.00%
Residual cash flows discount rate	7.00%	7.00%
Escrow earn rate	2.22%	2.17%
Loan assumption rate	0.00%	0.00%
Commercial Mortgage Backed Securities [Member] | Maximum [Member]
Servicing Assets at Fair Value [Line Items]
Expected defaults	2.00%	3.00%
Residual cash flows discount rate	15.00%	15.00%
Escrow earn rate	3.70%	3.45%
Loan assumption rate	3.18%	2.84%
Commercial Mortgage Backed Securities [Member] | Weighted Average [Member]
Servicing Assets at Fair Value [Line Items]
Expected defaults	1.14%	1.18%
Residual cash flows discount rate	9.19%	8.99%
Escrow earn rate	2.98%	2.84%
Loan assumption rate	1.39%	1.18%
Residential Mortgage Backed Securities [Member] | Minimum [Member]
Servicing Assets at Fair Value [Line Items]
Expected defaults	7.50%	8.50%
Prepayment speed	9.32%	8.37%
Servicing cost	$ 62,000,000	$ 76,000,000
Residential Mortgage Backed Securities [Member] | Maximum [Member]
Servicing Assets at Fair Value [Line Items]
Expected defaults	10.00%	11.00%
Prepayment speed	58.76%	48.63%
Servicing cost	$ 4,375,000,000	$ 4,385,000,000
Residential Mortgage Backed Securities [Member] | Weighted Average [Member]
Servicing Assets at Fair Value [Line Items]
Expected defaults	7.54%	8.54%
Prepayment speed	9.93%	9.12%
Servicing cost	$ 68,230,000	$ 83,050,000