Mortgage Servicing Assets - Schedule of Range and Weighted-Average of Significant Unobservable Inputs (Details) - Discounted Cash Flow [Member] - USD ($)	6 Months Ended
	Jun. 30, 2019	Jun. 30, 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	1.92%	2.40%
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	11.54%	15.00%
Escrow earn rate	3.13%	3.82%
Loan assumption rate	3.02%	3.00%
Commercial Mortgage Backed Securities [Member] | Weighted Average [Member]
Servicing Assets at Fair Value [Line Items]
Expected defaults	1.13%	1.17%
Residual cash flows discount rate	9.26%	9.06%
Escrow earn rate	2.63%	3.10%
Loan assumption rate	1.40%	1.19%
Residential Mortgage Backed Securities [Member] | Minimum [Member]
Servicing Assets at Fair Value [Line Items]
Expected defaults	7.50%	8.50%
Prepayment speed	10.95%	8.39%
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	62.06%	49.39%
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	7.53%	8.54%
Prepayment speed	12.52%	9.17%
Servicing cost	$ 67,550,000	$ 82,380,000