Loans Receivable, Net (Details - Modifications Types and Financial Impact) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) loan	Dec. 31, 2016 USD ($) loan	Dec. 31, 2015 USD ($) loan
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts | loan	334	565	401
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 40	$ 54	$ 37
Principal Forgiveness [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Post-Modification Recorded Investment	0	1	0
Payment Deferral [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Post-Modification Recorded Investment	0	0	1
Re-Age Extension or Interest Capitalization with Interest Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Post-Modification Recorded Investment	25	16	12
Other with Interest Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Post-Modification Recorded Investment	2	5	2
Other without Interest Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 13	$ 32	$ 22
One- To Four-Family [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts | loan	40	47	34
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 18	$ 18	$ 13
One- To Four-Family [Member] | Principal Forgiveness [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Post-Modification Recorded Investment	0	1	0
One- To Four-Family [Member] | Payment Deferral [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Post-Modification Recorded Investment	0	0	1
One- To Four-Family [Member] | Re-Age Extension or Interest Capitalization with Interest Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Post-Modification Recorded Investment	13	8	9
One- To Four-Family [Member] | Other with Interest Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Post-Modification Recorded Investment	1	2	0
One- To Four-Family [Member] | Other without Interest Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 4	$ 7	$ 3
Home Equity [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts | loan	294	518	367
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 22	$ 36	$ 24
Home Equity [Member] | Principal Forgiveness [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Post-Modification Recorded Investment	0	0	0
Home Equity [Member] | Payment Deferral [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Post-Modification Recorded Investment	0	0	0
Home Equity [Member] | Re-Age Extension or Interest Capitalization with Interest Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Post-Modification Recorded Investment	12	8	3
Home Equity [Member] | Other with Interest Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Post-Modification Recorded Investment	1	3	2
Home Equity [Member] | Other without Interest Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 9	$ 25	$ 19