Loans (Analysis of Impaired Loans) (Details) - Loans, Excluding Purchased Credit Impaired Loans [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	$ 8,377,258		$ 8,252,647
Recorded Investment of Loans Individually Measured for Specific Impairment	55,283		49,104
Recorded Investment	43,805		35,753
Unpaid Principal Balance	50,113		40,716
Related Allowance	2,911		2,132
Average Recorded Investment Impaired Loans	52,193	$ 70,577
Interest Recognized on Impaired Loans	189	239
Secured Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	3,351,027		3,286,416
Recorded Investment of Loans Individually Measured for Specific Impairment	30,207		26,285
Recorded Investment	5,426		6,350
Unpaid Principal Balance	6,189		8,460
Related Allowance	2,829		2,023
Average Recorded Investment Impaired Loans	28,246	42,306
Interest Recognized on Impaired Loans	12	12
Unsecured Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	115,199		112,097
Recorded Investment of Loans Individually Measured for Specific Impairment	18		20
Recorded Investment	0		20
Unpaid Principal Balance	0		20
Related Allowance	0		0
Average Recorded Investment Impaired Loans	19	24
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	281,466		235,138
Recorded Investment of Loans Individually Measured for Specific Impairment	864		888
Recorded Investment	313		325
Unpaid Principal Balance	793		798
Related Allowance	8		8
Average Recorded Investment Impaired Loans	876	881
Interest Recognized on Impaired Loans	6	7
Commercial Land [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	292,055		283,451
Recorded Investment of Loans Individually Measured for Specific Impairment	2,865		2,226
Recorded Investment	0		0
Unpaid Principal Balance	0		0
Related Allowance	0		0
Average Recorded Investment Impaired Loans	2,546	2,569
Interest Recognized on Impaired Loans	7	0
Income Property Multifamily [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	1,961,287		1,917,522
Recorded Investment of Loans Individually Measured for Specific Impairment	1,322		2,954
Recorded Investment	0		99
Unpaid Principal Balance	0		165
Related Allowance	0		1
Average Recorded Investment Impaired Loans	2,138	4,292
Interest Recognized on Impaired Loans	19	31
Owner Occupied [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	1,622,007		1,605,042
Recorded Investment of Loans Individually Measured for Specific Impairment	16,552		12,709
Recorded Investment	3,181		3,231
Unpaid Principal Balance	4,640		4,666
Related Allowance	52		69
Average Recorded Investment Impaired Loans	14,630	8,622
Interest Recognized on Impaired Loans	118	84
Land And Acquisition [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	3,619		4,417
Recorded Investment of Loans Individually Measured for Specific Impairment	0		0
Recorded Investment	0		0
Unpaid Principal Balance	0		0
Related Allowance	0		0
Residential Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	203,318		212,396
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	1,210
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	163,674		194,912
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	74,736		87,063
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	4,050
Interest Recognized on Impaired Loans	0	51
Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment of Loans Collectively Measured for Contingency Provision	308,870		314,193
Recorded Investment of Loans Individually Measured for Specific Impairment	3,455		4,022
Recorded Investment	2,558		3,326
Unpaid Principal Balance	2,703		3,584
Related Allowance	22		31
Average Recorded Investment Impaired Loans	3,738	6,623
Interest Recognized on Impaired Loans	27	$ 54
Impaired Loans With Recorded Allowance [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	11,478		13,351
Unpaid Principal Balance	14,325		17,693
Impaired Loans Without Recorded Allowance [Member] | Secured Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	24,781		19,935
Unpaid Principal Balance	30,656		24,404
Impaired Loans Without Recorded Allowance [Member] | Unsecured Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	18		0
Unpaid Principal Balance	18		0
Impaired Loans Without Recorded Allowance [Member] | One-to-Four Family Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	551		563
Unpaid Principal Balance	568		575
Impaired Loans Without Recorded Allowance [Member] | Commercial Land [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	2,865		2,226
Unpaid Principal Balance	2,909		2,272
Impaired Loans Without Recorded Allowance [Member] | Income Property Multifamily [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	1,322		2,855
Unpaid Principal Balance	1,333		3,011
Impaired Loans Without Recorded Allowance [Member] | Owner Occupied [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	13,371		9,478
Unpaid Principal Balance	13,617		9,750
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	0		0
Unpaid Principal Balance	0		0
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	0		0
Unpaid Principal Balance	0		0
Impaired Loans Without Recorded Allowance [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment	897		696
Unpaid Principal Balance	$ 1,012		$ 704