Loans (Analysis of Impaired Loans) (Details) - Loans, Excluding Purchased Credit Impaired Loans [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	$ 8,353,691		$ 8,353,691		$ 8,176,782
Recorded Investment of Loans Individually Measured for Specific Impairment	64,690		64,690		69,205
Recorded Investment	49,865		49,865		56,357
Unpaid Principal Balance	55,431		55,431		64,735
Related Allowance	1,255		1,255		2,360
Average Recorded Investment Impaired Loans	68,528	$ 42,623	69,552	$ 33,508
Interest Recognized on Impaired Loans	314	374	813	664
Secured Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	3,379,535		3,379,535		3,195,649
Recorded Investment of Loans Individually Measured for Specific Impairment	40,776		40,776		40,012
Recorded Investment	7,402		7,402		3,808
Unpaid Principal Balance	7,875		7,875		3,937
Related Allowance	1,139		1,139		1,867
Average Recorded Investment Impaired Loans	43,805	22,395	43,055	15,349
Interest Recognized on Impaired Loans	2	2	43	25
Unsecured Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	118,897		118,897		124,150
Recorded Investment of Loans Individually Measured for Specific Impairment	22		22		25
Recorded Investment	0		0		25
Unpaid Principal Balance	0		0		24
Related Allowance	0		0		3
Average Recorded Investment Impaired Loans	444	0	234	0
Interest Recognized on Impaired Loans	0	0	1	0
One-to-Four Family Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	230,915		230,915		185,659
Recorded Investment of Loans Individually Measured for Specific Impairment	396		396		895
Recorded Investment	337		337		867
Unpaid Principal Balance	606		606		1,408
Related Allowance	8		8		103
Average Recorded Investment Impaired Loans	545	856	713	688
Interest Recognized on Impaired Loans	12	15	30	37
Commercial Land [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	279,008		279,008		293,694
Recorded Investment of Loans Individually Measured for Specific Impairment	2,230		2,230		2,287
Recorded Investment	0		0		0
Unpaid Principal Balance	0		0		0
Related Allowance	0		0		0
Average Recorded Investment Impaired Loans	2,246	2,549	2,407	2,026
Interest Recognized on Impaired Loans	26	0	26	0
Income Property Multifamily [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	1,884,936		1,884,936		1,901,313
Recorded Investment of Loans Individually Measured for Specific Impairment	2,754		2,754		5,023
Recorded Investment	110		110		2,768
Unpaid Principal Balance	175		175		3,328
Related Allowance	1		1		185
Average Recorded Investment Impaired Loans	2,443	4,214	3,367	4,137
Interest Recognized on Impaired Loans	34	21	96	27
Owner Occupied [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	1,587,550		1,587,550		1,591,298
Recorded Investment of Loans Individually Measured for Specific Impairment	9,719		9,719		8,688
Recorded Investment	3,274		3,274		77
Unpaid Principal Balance	4,693		4,693		80
Related Allowance	71		71		3
Average Recorded Investment Impaired Loans	9,349	4,530	8,986	4,496
Interest Recognized on Impaired Loans	124	127	333	319
Land And Acquisition [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	5,963		5,963		9,907
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	4
Interest Recognized on Impaired Loans	0	0	0	0
Residential Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	204,628		204,628		188,481
Recorded Investment of Loans Individually Measured for Specific Impairment	0		0		1,210
Recorded Investment	0		0		0
Unpaid Principal Balance	0		0		0
Related Allowance	0		0		0
Average Recorded Investment Impaired Loans	0	0	605	84
Interest Recognized on Impaired Loans	0	0	0	0
Income Property Multifamily Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	253,636		253,636		293,028
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, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	86,461		86,461		68,393
Recorded Investment of Loans Individually Measured for Specific Impairment	4,050		4,050		4,050
Recorded Investment	0		0		0
Unpaid Principal Balance	0		0		0
Related Allowance	0		0		0
Average Recorded Investment Impaired Loans	4,050	2,025	4,050	1,012
Interest Recognized on Impaired Loans	72	151	174	151
Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	322,162		322,162		325,210
Recorded Investment of Loans Individually Measured for Specific Impairment	4,743		4,743		7,015
Recorded Investment	3,702		3,702		5,303
Unpaid Principal Balance	3,953		3,953		5,568
Related Allowance	36		36		199
Average Recorded Investment Impaired Loans	5,646	6,054	6,135	5,712
Interest Recognized on Impaired Loans	44	$ 58	110	$ 105
Impaired Loans With Recorded Allowance [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	14,825		14,825		12,848
Unpaid Principal Balance	17,302		17,302		14,345
Impaired Loans Without Recorded Allowance [Member] | Secured Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	33,374		33,374		36,204
Unpaid Principal Balance	38,293		38,293		42,314
Impaired Loans Without Recorded Allowance [Member] | Unsecured Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	22		22		0
Unpaid Principal Balance	21		21		0
Impaired Loans Without Recorded Allowance [Member] | One-to-Four Family Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	59		59		28
Unpaid Principal Balance	256		256		337
Impaired Loans Without Recorded Allowance [Member] | Commercial Land [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	2,230		2,230		2,287
Unpaid Principal Balance	2,274		2,274		2,282
Impaired Loans Without Recorded Allowance [Member] | Income Property Multifamily [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	2,644		2,644		2,255
Unpaid Principal Balance	2,789		2,789		2,601
Impaired Loans Without Recorded Allowance [Member] | Owner Occupied [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	6,445		6,445		8,611
Unpaid Principal Balance	6,692		6,692		10,077
Impaired Loans Without Recorded Allowance [Member] | Land And Acquisition [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	0		0		0
Unpaid Principal Balance	0		0		0
Impaired Loans Without Recorded Allowance [Member] | Residential Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	0		0		1,210
Unpaid Principal Balance	0		0		1,210
Impaired Loans Without Recorded Allowance [Member] | Income Property Multifamily Construction [Member]
Financing Receivable, Recorded Investment [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, Recorded Investment [Line Items]
Recorded Investment	4,050		4,050		4,050
Unpaid Principal Balance	4,050		4,050		4,050
Impaired Loans Without Recorded Allowance [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	1,041		1,041		1,712
Unpaid Principal Balance	$ 1,056		$ 1,056		$ 1,864