Fair Value Disclosures (Details - Recurring and Nonrecurring) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	$ 20,679,000	$ 13,892,000
Assets measured at fair value on recurring basis percentage of total assets	33.00%	29.00%
Fair Value, Transfers Between Level 1 and Level 2 and Level 3, Description and Policy (Textuals) [Abstract]
Fair value, assets, Level 1 to Level 2 transfers, amount	$ 0	$ 0
Fair value, assets, Level 2 to Level 1 transfers, amount	0	0
Fair value, liabilities, Level 1 to Level 2 transfers, amount	0	0
Fair value, liabilities, Level 2 to Level 1 transfers, amount	0	0
Fair value, assets, Level 1 to Level 3 transfers, amount	0	0
Fair value, assets, Level 3 to Level 1 transfers, amount	0	0
Fair value, assets, Level 2 to Level 3 transfers, amount	0	0
Fair value, assets, Level 3 to Level 2 transfers, amount	0	0
Fair value, liabilities, Level 1 to Level 3 transfers, amount	0	0
Fair value, liabilities, Level 3 to Level 1 transfers, amount	0	0
Fair value, liabilities, Level 2 to Level 3 transfers, amount	0	0
Fair value, liabilities, Level 3 to Level 2 transfers, amount	$ 0	$ 0
Less than [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities measured at fair value on recurring basis percentage of total liabilities	1.00%	1.00%
Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	$ 20,679,000	$ 13,892,000
U.S. Treasuries	300,000
Derivative assets	131,000	165,000
Total assets measured at fair value on a recurring basis	21,110,000	14,057,000
Derivative Liability	14,000	31,000
Total liabilities measured at fair value on a recurring basis	14,000	31,000
Fair Value, Measurements, Nonrecurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total loans receivable	35,000	46,000
Loans Held-for-sale, Fair Value Disclosure	17,000
REO	26,000	35,000
Total Assets Measured at Fair Value On A Nonrecurring Basis	78,000	81,000
Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	7,000	7,000
U.S. Treasuries	300,000
Total assets measured at fair value on a recurring basis	307,000	7,000
Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	20,672,000	13,885,000
Derivative assets	131,000	165,000
Total assets measured at fair value on a recurring basis	20,803,000	14,050,000
Derivative Liability	14,000	31,000
Total liabilities measured at fair value on a recurring basis	14,000	31,000
Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Loans Held-for-sale, Fair Value Disclosure	17,000
Total Assets Measured at Fair Value On A Nonrecurring Basis	17,000
Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total loans receivable	35,000	46,000
REO	26,000	35,000
Total Assets Measured at Fair Value On A Nonrecurring Basis	61,000	81,000
Loans Receivable [Member]
Gains Losses On Nonrecurring Fair Value Measurements [Abstract]
(Gains) losses measured at fair value	9,000	16,000	$ 21,000
One- To Four-Family [Member] | Loans Receivable [Member]
Gains Losses On Nonrecurring Fair Value Measurements [Abstract]
(Gains) losses measured at fair value	4,000	4,000	7,000
One- To Four-Family [Member] | Loans Receivable [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total loans receivable	22,000	25,000
One- To Four-Family [Member] | Loans Receivable [Member] | Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total loans receivable	22,000	25,000
Home Equity [Member] | Loans Receivable [Member]
Gains Losses On Nonrecurring Fair Value Measurements [Abstract]
(Gains) losses measured at fair value	5,000	12,000	$ 14,000
Home Equity [Member] | Loans Receivable [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total loans receivable	13,000	21,000
Home Equity [Member] | Loans Receivable [Member] | Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total loans receivable	13,000	21,000
Debt Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	20,672,000	13,885,000
Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	20,672,000	13,885,000
Debt Securities [Member] | Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	20,672,000	13,885,000
Agency mortgage-backed securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	19,195,000	12,634,000
Agency mortgage-backed securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	19,195,000	12,634,000
Agency mortgage-backed securities [Member] | Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	19,195,000	12,634,000
Agency Debentures [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	966,000	788,000
Agency Debentures [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	966,000	788,000
Agency Debentures [Member] | Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	966,000	788,000
U.S. Treasuries [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	458,000	407,000
U.S. Treasuries [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	458,000	407,000
U.S. Treasuries [Member] | Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	458,000	407,000
Agency Debt Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	33,000	24,000
Agency Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	33,000	24,000
Agency Debt Securities [Member] | Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	33,000	24,000
Municipal Bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	20,000	32,000
Municipal Bonds [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	20,000	32,000
Municipal Bonds [Member] | Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	20,000	32,000
Equity Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	7,000	7,000
Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	7,000	7,000
Equity Securities [Member] | Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	$ 7,000	$ 7,000