Fair Value - Level 3 Unobservable Inputs, Mortgage Loans and IRLC (Details) - item	Mar. 31, 2019	Dec. 31, 2018
Mortgage loans held for sale | Discount rate | Level 3 | Minimum
Excess servicing spread financing
Input	3.1	2.8
Mortgage loans held for sale | Discount rate | Level 3 | Maximum
Excess servicing spread financing
Input	9.2	9.2
Mortgage loans held for sale | Discount rate | Level 3 | Weighted average
Excess servicing spread financing
Input	3.1	2.9
Mortgage loans held for sale | Twelve-month projected housing price index Change | Level 3 | Minimum
Excess servicing spread financing
Input	3.0	2.2
Mortgage loans held for sale | Twelve-month projected housing price index Change | Level 3 | Maximum
Excess servicing spread financing
Input	4.8	5.0
Mortgage loans held for sale | Twelve-month projected housing price index Change | Level 3 | Weighted average
Excess servicing spread financing
Input	3.3	3.5
Mortgage loans held for sale | Prepayment/resale speed | Level 3 | Minimum
Excess servicing spread financing
Input	0.1	0.1
Mortgage loans held for sale | Prepayment/resale speed | Level 3 | Maximum
Excess servicing spread financing
Input	24.3	21.8
Mortgage loans held for sale | Prepayment/resale speed | Level 3 | Weighted average
Excess servicing spread financing
Input	22.0	20.1
Mortgage loans held for sale | Total prepayment speed | Level 3 | Minimum
Excess servicing spread financing
Input	0.1	0.1
Mortgage loans held for sale | Total prepayment speed | Level 3 | Maximum
Excess servicing spread financing
Input	42.0	40.5
Mortgage loans held for sale | Total prepayment speed | Level 3 | Weighted average
Excess servicing spread financing
Input	39.2	37.7
Interest rate lock commitments | Pull-through rate | Level 3 | Minimum
Excess servicing spread financing
Input	12.2	16.6
Interest rate lock commitments | Pull-through rate | Level 3 | Maximum
Excess servicing spread financing
Input	100.0	100.0
Interest rate lock commitments | Pull-through rate | Level 3 | Weighted average
Excess servicing spread financing
Input	82.8	84.1
Interest rate lock commitments | Mortgage servicing rights value expressed as servicing fee multiple | Level 3 | Minimum
Excess servicing spread financing
Input	1.1	1.5
Interest rate lock commitments | Mortgage servicing rights value expressed as servicing fee multiple | Level 3 | Maximum
Excess servicing spread financing
Input	5.7	5.5
Interest rate lock commitments | Mortgage servicing rights value expressed as servicing fee multiple | Level 3 | Weighted average
Excess servicing spread financing
Input	3.8	3.8
Interest rate lock commitments | Percentage of unpaid principal balance | Level 3 | Minimum
Excess servicing spread financing
Input	0.3	0.4
Interest rate lock commitments | Percentage of unpaid principal balance | Level 3 | Maximum
Excess servicing spread financing
Input	2.7	3.2
Interest rate lock commitments | Percentage of unpaid principal balance | Level 3 | Weighted average
Excess servicing spread financing
Input	1.5	1.5
Repurchase agreement derivatives
Excess servicing spread financing
Acceptance rate (as a percent)	97.00%	97.00%