Segment Information (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) segment	Jun. 30, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment			3
Summary of Operations
Net interest income	$ 97	$ 77	$ 180	$ 156
Net gain (loss) on loan sales	66	90	114	165
Representation and warranty benefit	3	4	7	6
Other noninterest income	47	34	95	62
Total net interest income and noninterest income	213	205	396	389
(Provision) benefit for loan losses	1	3	(2)	16
Depreciation and amortization expense	(9)	(8)	(18)	(15)
Other noninterest expense	(145)	(131)	(276)	(261)
Total noninterest expense	(154)	(139)	(294)	(276)
Income before income taxes	60	69	100	129
Provision for income taxes	19	22	32	43
Net income	41	47	68	86
Average balances
Loans held-for-sale	4,269	2,884	3,780	2,897
Loans with government guarantees	295	444	318	460
Loans held-for-investment	6,224	5,569	5,933	5,618
Total assets	15,710	13,438	14,881	13,491
Deposits	8,739	8,631	8,767	8,341
Intersegment Eliminations
Summary of Operations
Total net interest income and noninterest income	0	0	0	0
Community Banking
Summary of Operations
Net interest income	57	49	108	96
Net gain (loss) on loan sales	(1)	3	(3)	9
Representation and warranty benefit	0	0	0	0
Other noninterest income	6	6	14	13
Total net interest income and noninterest income	62	58	119	118
(Provision) benefit for loan losses	0	3	(2)	16
Depreciation and amortization expense	(2)	(2)	(4)	(4)
Other noninterest expense	(45)	(45)	(89)	(88)
Total noninterest expense	(47)	(47)	(93)	(92)
Income before income taxes	15	14	24	42
Provision for income taxes	5	5	8	15
Net income	10	9	16	27
Average balances
Loans held-for-sale	15	56	18	117
Loans with government guarantees	0	0	0	0
Loans held-for-investment	6,188	5,566	5,898	5,611
Total assets	6,255	5,653	5,966	5,745
Deposits	7,362	7,073	7,408	6,984
Community Banking | Intersegment Eliminations
Summary of Operations
Total net interest income and noninterest income	0	0	(1)	(1)
Mortgage Originations
Summary of Operations
Net interest income	32	21	62	43
Net gain (loss) on loan sales	67	87	117	156
Representation and warranty benefit	3	4	7	6
Other noninterest income	21	9	43	11
Total net interest income and noninterest income	123	121	229	216
(Provision) benefit for loan losses	0	0	(2)	0
Depreciation and amortization expense	(1)	(1)	(3)	(2)
Other noninterest expense	(75)	(62)	(137)	(122)
Total noninterest expense	(76)	(63)	(140)	(124)
Income before income taxes	47	58	87	92
Provision for income taxes	17	20	31	32
Net income	30	38	56	60
Average balances
Loans held-for-sale	4,254	2,828	3,762	2,780
Loans with government guarantees	295	444	318	460
Loans held-for-investment	7	3	6	7
Total assets	5,562	4,109	5,085	4,071
Deposits	0	0	0	0
Mortgage Originations | Intersegment Eliminations
Summary of Operations
Total net interest income and noninterest income	1	0	1	0
Mortgage Servicing
Summary of Operations
Net interest income	4	6	9	10
Net gain (loss) on loan sales	0	0	0	0
Representation and warranty benefit	0	0	0	0
Other noninterest income	15	13	29	28
Total net interest income and noninterest income	19	19	38	38
(Provision) benefit for loan losses	0	0	0	0
Depreciation and amortization expense	(1)	(1)	(2)	(2)
Other noninterest expense	(24)	(21)	(49)	(45)
Total noninterest expense	(25)	(22)	(51)	(47)
Income before income taxes	(6)	(3)	(13)	(9)
Provision for income taxes	(3)	(1)	(5)	(3)
Net income	(3)	(2)	(8)	(6)
Average balances
Loans held-for-sale	0	0		0
Loans with government guarantees	0	0	0	0
Loans held-for-investment	0	0	0	0
Total assets	39	40	40	41
Deposits	1,377	1,558	1,359	1,357
Mortgage Servicing | Intersegment Eliminations
Summary of Operations
Total net interest income and noninterest income	3	6	9	12
Other
Summary of Operations
Net interest income	4	1	1	7
Net gain (loss) on loan sales	0	0	0	0
Representation and warranty benefit	0	0	0	0
Other noninterest income	5	6	9	10
Total net interest income and noninterest income	9	7	10	17
(Provision) benefit for loan losses	1	0	2	0
Depreciation and amortization expense	(5)	(4)	(9)	(7)
Other noninterest expense	(1)	(3)	(1)	(6)
Total noninterest expense	(6)	(7)	(10)	(13)
Income before income taxes	4	0	2	4
Provision for income taxes	0	(2)	(2)	(1)
Net income	4	2	4	5
Average balances
Loans held-for-sale	0	0	0	0
Loans with government guarantees	0	0	0	0
Loans held-for-investment	29	0	29	0
Total assets	3,854	3,636	3,790	3,634
Deposits	0	0	0	0
Other | Intersegment Eliminations
Summary of Operations
Total net interest income and noninterest income	$ (4)	$ (6)	$ (9)	$ (11)