Loans (Analysis of Impaired Loans) (Details) - Loans, Excluding Purchased Credit Impaired Loans [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	$ 8,158,383		$ 8,176,782
Recorded Investment of Loans Individually Measured for Specific Impairment	71,949		69,205
Recorded Investment	48,824		56,357
Unpaid Principal Balance	52,674		64,735
Related Allowance	5,857		2,360
Average Recorded Investment Impaired Loans	70,577	$ 24,394
Interest Recognized on Impaired Loans	239	49
Secured Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	3,221,659		3,195,649
Recorded Investment of Loans Individually Measured for Specific Impairment	44,600		40,012
Recorded Investment	13,836		3,808
Unpaid Principal Balance	18,931		3,937
Related Allowance	5,657		1,867
Average Recorded Investment Impaired Loans	42,306	8,303
Interest Recognized on Impaired Loans	12	19
Unsecured Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	120,056		124,150
Recorded Investment of Loans Individually Measured for Specific Impairment	23		25
Recorded Investment	23		25
Unpaid Principal Balance	23		24
Related Allowance	2		3
Average Recorded Investment Impaired Loans	24	0
Interest Recognized on Impaired Loans	0	0
One-to-Four Family Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	179,700		185,659
Recorded Investment of Loans Individually Measured for Specific Impairment	868		895
Recorded Investment	428		867
Unpaid Principal Balance	715		1,408
Related Allowance	22		103
Average Recorded Investment Impaired Loans	881	521
Interest Recognized on Impaired Loans	7	2
Commercial Land [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	286,613		293,694
Recorded Investment of Loans Individually Measured for Specific Impairment	2,851		2,287
Recorded Investment	0		0
Unpaid Principal Balance	0		0
Related Allowance	0		0
Average Recorded Investment Impaired Loans	2,569	1,504
Interest Recognized on Impaired Loans	0	0
Income Property Multifamily [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	1,870,614		1,901,313
Recorded Investment of Loans Individually Measured for Specific Impairment	3,560		5,023
Recorded Investment	0		2,768
Unpaid Principal Balance	0		3,328
Related Allowance	0		185
Average Recorded Investment Impaired Loans	4,292	4,059
Interest Recognized on Impaired Loans	31	1
Owner Occupied [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	1,582,385		1,591,298
Recorded Investment of Loans Individually Measured for Specific Impairment	8,556		8,688
Recorded Investment	3,399		77
Unpaid Principal Balance	4,821		80
Related Allowance	5		3
Average Recorded Investment Impaired Loans	8,622	4,462
Interest Recognized on Impaired Loans	84	0
Land And Acquisition [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	6,540		9,907
Recorded Investment of Loans Individually Measured for Specific Impairment	0		0
Recorded Investment	0		0
Unpaid Principal Balance	0		0
Related Allowance	0		0
Average Recorded Investment Impaired Loans	0	7
Interest Recognized on Impaired Loans	0	0
Residential Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	199,868		188,481
Recorded Investment of Loans Individually Measured for Specific Impairment	1,210		1,210
Recorded Investment	0		0
Unpaid Principal Balance	0		0
Related Allowance	0		0
Average Recorded Investment Impaired Loans	1,210	168
Interest Recognized on Impaired Loans	0	0
Income Property Multifamily Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	306,137		293,028
Recorded Investment of Loans Individually Measured for Specific Impairment	0		0
Recorded Investment	0		0
Unpaid Principal Balance	0		0
Related Allowance	0		0
Owner Occupied Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	68,966		68,393
Recorded Investment of Loans Individually Measured for Specific Impairment	4,050		4,050
Recorded Investment	0		0
Unpaid Principal Balance	0		0
Related Allowance	0		0
Average Recorded Investment Impaired Loans	4,050	0
Interest Recognized on Impaired Loans	51	0
Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	315,845		325,210
Recorded Investment of Loans Individually Measured for Specific Impairment	6,231		7,015
Recorded Investment	5,439		5,303
Unpaid Principal Balance	5,707		5,568
Related Allowance	171		199
Average Recorded Investment Impaired Loans	6,623	5,370
Interest Recognized on Impaired Loans	54	$ 27
Impaired Loans With Recorded Allowance [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	23,125		12,848
Unpaid Principal Balance	30,197		14,345
Impaired Loans Without Recorded Allowance [Member] | Secured Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	30,764		36,204
Unpaid Principal Balance	33,785		42,314
Impaired Loans Without Recorded Allowance [Member] | Unsecured Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	0		0
Unpaid Principal Balance	0		0
Impaired Loans Without Recorded Allowance [Member] | One-to-Four Family Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	440		28
Unpaid Principal Balance	1,017		337
Impaired Loans Without Recorded Allowance [Member] | Commercial Land [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	2,851		2,287
Unpaid Principal Balance	2,860		2,282
Impaired Loans Without Recorded Allowance [Member] | Income Property Multifamily [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	3,560		2,255
Unpaid Principal Balance	3,623		2,601
Impaired Loans Without Recorded Allowance [Member] | Owner Occupied [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	5,157		8,611
Unpaid Principal Balance	5,269		10,077
Impaired Loans Without Recorded Allowance [Member] | Land And Acquisition [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	0		0
Unpaid Principal Balance	0		0
Impaired Loans Without Recorded Allowance [Member] | Residential Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	1,210		1,210
Unpaid Principal Balance	1,210		1,210
Impaired Loans Without Recorded Allowance [Member] | Income Property Multifamily Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	0		0
Unpaid Principal Balance	0		0
Impaired Loans Without Recorded Allowance [Member] | Owner Occupied Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	4,050		4,050
Unpaid Principal Balance	4,050		4,050
Impaired Loans Without Recorded Allowance [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	792		1,712
Unpaid Principal Balance	$ 860		$ 1,864