Loans (Analysis of Impaired Loans) (Details) - Loans, Excluding Purchased Credit Impaired Loans [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Financing Receivable, Credit Quality Indicator [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	$ 8,633,361		$ 8,633,361		$ 8,252,647
Recorded Investment of Loans Individually Measured for Specific Impairment	41,217		41,217		49,104
Recorded Investment	26,040		26,040		35,753
Unpaid Principal Balance	30,960		30,960		40,716
Related Allowance	2,326		2,326		2,132
Average Recorded Investment Impaired Loans	38,638	$ 68,528	45,416	$ 69,552
Interest Recognized on Impaired Loans	314	314	558	813
Secured Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	3,530,404		3,530,404		3,286,416
Recorded Investment of Loans Individually Measured for Specific Impairment	25,579		25,579		26,285
Recorded Investment	9,114		9,114		6,350
Unpaid Principal Balance	10,673		10,673		8,460
Related Allowance	1,879		1,879		2,023
Average Recorded Investment Impaired Loans	21,419	43,805	24,833	43,055
Interest Recognized on Impaired Loans	108	2	267	43
Unsecured Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	139,360		139,360		112,097
Recorded Investment of Loans Individually Measured for Specific Impairment	13		13		20
Recorded Investment	13		13		20
Unpaid Principal Balance	13		13		20
Related Allowance	0		0		0
Average Recorded Investment Impaired Loans	15	444	17	234
Interest Recognized on Impaired Loans	0	0	1	1
One-to-Four Family Residential [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	272,686		272,686		235,138
Recorded Investment of Loans Individually Measured for Specific Impairment	347		347		888
Recorded Investment	347		347		325
Unpaid Principal Balance	635		635		798
Related Allowance	5		5		8
Average Recorded Investment Impaired Loans	596	545	736	713
Interest Recognized on Impaired Loans	12	12	29	30
Commercial Land [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	292,436		292,436		283,451
Recorded Investment of Loans Individually Measured for Specific Impairment	2,860		2,860		2,226
Recorded Investment	1,591		1,591		0
Unpaid Principal Balance	1,601		1,601		0
Related Allowance	320		320		0
Average Recorded Investment Impaired Loans	2,861	2,246	2,704	2,407
Interest Recognized on Impaired Loans	8	26	23	26
Income Property Multifamily [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	1,961,935		1,961,935		1,917,522
Recorded Investment of Loans Individually Measured for Specific Impairment	0		0		2,954
Recorded Investment	0		0		99
Unpaid Principal Balance	0		0		165
Related Allowance	0		0		1
Average Recorded Investment Impaired Loans	664	2,443	1,401	3,367
Interest Recognized on Impaired Loans	0	34	0	96
Owner Occupied [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	1,688,118		1,688,118		1,605,042
Recorded Investment of Loans Individually Measured for Specific Impairment	10,190		10,190		12,709
Recorded Investment	3,733		3,733		3,231
Unpaid Principal Balance	5,260		5,260		4,666
Related Allowance	105		105		69
Average Recorded Investment Impaired Loans	10,241	9,349	12,435	8,986
Interest Recognized on Impaired Loans	176	124	210	333
Land And Acquisition [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	1,614		1,614		4,417
Recorded Investment of Loans Individually Measured for Specific Impairment	0		0		0
Recorded Investment	0		0		0
Unpaid Principal Balance	0		0		0
Related Allowance	0		0		0
Residential Construction [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	192,563		192,563		212,396
Recorded Investment of Loans Individually Measured for Specific Impairment	0		0		0
Recorded Investment	0		0		0
Unpaid Principal Balance	0		0		0
Related Allowance	0		0		0
Average Recorded Investment Impaired Loans	0	0	0	605
Interest Recognized on Impaired Loans	0	0	0	0
Income Property Multifamily Construction [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	157,400		157,400		194,912
Recorded Investment of Loans Individually Measured for Specific Impairment	0		0		0
Recorded Investment	0		0		0
Unpaid Principal Balance	0		0		0
Related Allowance	0		0		0
Owner Occupied Construction [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	102,246		102,246		87,063
Recorded Investment of Loans Individually Measured for Specific Impairment	0		0		0
Recorded Investment	0		0		0
Unpaid Principal Balance	0		0		0
Related Allowance	0		0		0
Average Recorded Investment Impaired Loans	0	4,050	0	4,050
Interest Recognized on Impaired Loans	0	72	0	174
Consumer Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	294,599		294,599		314,193
Recorded Investment of Loans Individually Measured for Specific Impairment	2,228		2,228		4,022
Recorded Investment	379		379		3,326
Unpaid Principal Balance	514		514		3,584
Related Allowance	17		17		31
Average Recorded Investment Impaired Loans	2,842	5,646	3,290	6,135
Interest Recognized on Impaired Loans	10	$ 44	28	$ 110
Impaired Loans With Recorded Allowance [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Recorded Investment	15,177		15,177		13,351
Unpaid Principal Balance	18,696		18,696		17,693
Impaired Loans Without Recorded Allowance [Member] | Secured Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Recorded Investment	16,465		16,465		19,935
Unpaid Principal Balance	21,051		21,051		24,404
Impaired Loans Without Recorded Allowance [Member] | Unsecured Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Recorded Investment	0		0		0
Unpaid Principal Balance	0		0		0
Impaired Loans Without Recorded Allowance [Member] | One-to-Four Family Residential [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Recorded Investment	0		0		563
Unpaid Principal Balance	0		0		575
Impaired Loans Without Recorded Allowance [Member] | Commercial Land [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Recorded Investment	1,269		1,269		2,226
Unpaid Principal Balance	1,304		1,304		2,272
Impaired Loans Without Recorded Allowance [Member] | Income Property Multifamily [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Recorded Investment	0		0		2,855
Unpaid Principal Balance	0		0		3,011
Impaired Loans Without Recorded Allowance [Member] | Owner Occupied [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Recorded Investment	6,457		6,457		9,478
Unpaid Principal Balance	6,599		6,599		9,750
Impaired Loans Without Recorded Allowance [Member] | Land And Acquisition [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Recorded Investment	0		0		0
Unpaid Principal Balance	0		0		0
Impaired Loans Without Recorded Allowance [Member] | Residential Construction [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Recorded Investment	0		0		0
Unpaid Principal Balance	0		0		0
Impaired Loans Without Recorded Allowance [Member] | Income Property Multifamily Construction [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Recorded Investment	0		0		0
Unpaid Principal Balance	0		0		0
Impaired Loans Without Recorded Allowance [Member] | Owner Occupied Construction [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Recorded Investment	0		0		0
Unpaid Principal Balance	0		0		0
Impaired Loans Without Recorded Allowance [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Recorded Investment	1,849		1,849		696
Unpaid Principal Balance	$ 2,006		$ 2,006		$ 704