Loans (Analysis of Impaired Loans) (Details) - Loans, Excluding Purchased Credit Impaired Loans [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	$ 8,279,959		$ 8,279,959		$ 8,176,782
Recorded Investment of Loans Individually Measured for Specific Impairment	72,366		72,366		69,205
Recorded Investment	60,688		60,688		56,357
Unpaid Principal Balance	74,464		74,464		64,735
Related Allowance	256		256		2,360
Average Recorded Investment Impaired Loans	72,157	$ 31,500	71,173	$ 29,486
Interest Recognized on Impaired Loans	339	301	566	346
Secured Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	3,360,586		3,360,586		3,195,649
Recorded Investment of Loans Individually Measured for Specific Impairment	46,833		46,833		40,012
Recorded Investment	2,731		2,731		3,808
Unpaid Principal Balance	3,120		3,120		3,937
Related Allowance	67		67		1,867
Average Recorded Investment Impaired Loans	45,716	15,590	43,815	13,332
Interest Recognized on Impaired Loans	85	50	97	69
Unsecured Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	115,468		115,468		124,150
Recorded Investment of Loans Individually Measured for Specific Impairment	866		866		25
Recorded Investment	0		0		25
Unpaid Principal Balance	0		0		24
Related Allowance	0		0		3
Average Recorded Investment Impaired Loans	444	0	304	0
Interest Recognized on Impaired Loans	1	0	1	0
One-to-Four Family Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	178,121		178,121		185,659
Recorded Investment of Loans Individually Measured for Specific Impairment	693		693		895
Recorded Investment	346		346		867
Unpaid Principal Balance	742		742		1,408
Related Allowance	8		8		103
Average Recorded Investment Impaired Loans	780	648	818	608
Interest Recognized on Impaired Loans	12	21	18	22
Commercial Land [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	279,408		279,408		293,694
Recorded Investment of Loans Individually Measured for Specific Impairment	2,262		2,262		2,287
Recorded Investment	0		0		0
Unpaid Principal Balance	0		0		0
Related Allowance	0		0		0
Average Recorded Investment Impaired Loans	2,557	2,549	2,467	1,936
Interest Recognized on Impaired Loans	0	0	0	0
Income Property Multifamily [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	1,849,318		1,849,318		1,901,313
Recorded Investment of Loans Individually Measured for Specific Impairment	2,132		2,132		5,023
Recorded Investment	0		0		2,768
Unpaid Principal Balance	0		0		3,328
Related Allowance	0		0		185
Average Recorded Investment Impaired Loans	2,846	3,676	3,572	3,925
Interest Recognized on Impaired Loans	32	7	62	6
Owner Occupied [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	1,594,762		1,594,762		1,591,298
Recorded Investment of Loans Individually Measured for Specific Impairment	8,980		8,980		8,688
Recorded Investment	3,299		3,299		77
Unpaid Principal Balance	4,717		4,717		80
Related Allowance	86		86		3
Average Recorded Investment Impaired Loans	8,768	3,453	8,741	4,107
Interest Recognized on Impaired Loans	124	192	209	192
Land And Acquisition [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	6,570		6,570		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	5
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	198,673		198,673		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	605	0	807	112
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	302,801		302,801		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	75,644		75,644		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	0	4,050	0
Interest Recognized on Impaired Loans	51	0	102	0
Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	318,608		318,608		325,210
Recorded Investment of Loans Individually Measured for Specific Impairment	6,550		6,550		7,015
Recorded Investment	5,302		5,302		5,303
Unpaid Principal Balance	5,590		5,590		5,568
Related Allowance	95		95		199
Average Recorded Investment Impaired Loans	6,391	5,584	6,599	5,461
Interest Recognized on Impaired Loans	34	$ 31	77	$ 57
Impaired Loans With Recorded Allowance [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	11,678		11,678		12,848
Unpaid Principal Balance	14,169		14,169		14,345
Impaired Loans Without Recorded Allowance [Member] | Secured Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	44,102		44,102		36,204
Unpaid Principal Balance	53,050		53,050		42,314
Impaired Loans Without Recorded Allowance [Member] | Unsecured Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	866		866		0
Unpaid Principal Balance	4,906		4,906		0
Impaired Loans Without Recorded Allowance [Member] | One-to-Four Family Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	347		347		28
Unpaid Principal Balance	809		809		337
Impaired Loans Without Recorded Allowance [Member] | Commercial Land [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	2,262		2,262		2,287
Unpaid Principal Balance	2,277		2,277		2,282
Impaired Loans Without Recorded Allowance [Member] | Income Property Multifamily [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	2,132		2,132		2,255
Unpaid Principal Balance	2,195		2,195		2,601
Impaired Loans Without Recorded Allowance [Member] | Owner Occupied [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	5,681		5,681		8,611
Unpaid Principal Balance	5,858		5,858		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	1,248		1,248		1,712
Unpaid Principal Balance	$ 1,319		$ 1,319		$ 1,864