Loans (Analysis of Impaired Loans) (Details) - Loans, Excluding Purchased Credit Impaired Loans [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) Modifications	Dec. 31, 2016 USD ($) Modifications	Dec. 31, 2015 USD ($) Modifications
Financing Receivable, Modifications, Number of Contracts | Modifications	60	54	7
Recorded Investment of Loans Collectively Measured for Contingency Provision	$ 8,176,782	$ 6,042,304
Recorded Investment of Loans Individually Measured for Specific Impairment	69,205	25,459
Recorded Investment	5,303	4,464
Unpaid Principal Balance	5,568	4,558
Related Allowance	199	57
Impaired Financing Receivable, Average Recorded Investment	40,650	21,493	$ 22,372
Impaired Financing Receivable, Interest Income, Accrual Method	$ 971	$ 237	$ 202
Commercial business: Secured loans [Member]
Financing Receivable, Modifications, Number of Contracts | Modifications	10	9	5
Recorded Investment of Loans Collectively Measured for Contingency Provision	$ 3,195,649	$ 2,442,772
Recorded Investment of Loans Individually Measured for Specific Impairment	40,012	8,818
Recorded Investment	3,808	2,414
Unpaid Principal Balance	3,937	2,484
Related Allowance	1,867	664
Impaired Financing Receivable, Average Recorded Investment	20,282	9,368	$ 7,987
Impaired Financing Receivable, Interest Income, Accrual Method	$ 60	$ 79	$ 84
Commercial business: Unsecured loans [Member]
Financing Receivable, Modifications, Number of Contracts | Modifications	1	0	0
Recorded Investment of Loans Collectively Measured for Contingency Provision	$ 124,150	$ 94,737
Recorded Investment of Loans Individually Measured for Specific Impairment	25	0
Recorded Investment	25	0
Unpaid Principal Balance	24	0
Related Allowance	3	0
Impaired Financing Receivable, Average Recorded Investment	5	0	$ 0
Impaired Financing Receivable, Interest Income, Accrual Method	$ 0	$ 0	$ 0
Real estate: One-to-four family residential [Member]
Financing Receivable, Modifications, Number of Contracts | Modifications	3	3	1
Recorded Investment of Loans Collectively Measured for Contingency Provision	$ 185,659	$ 167,403
Recorded Investment of Loans Individually Measured for Specific Impairment	895	529
Recorded Investment	867	435
Unpaid Principal Balance	1,408	693
Related Allowance	103	12
Impaired Financing Receivable, Average Recorded Investment	730	743	$ 2,848
Impaired Financing Receivable, Interest Income, Accrual Method	$ 49	$ 10	$ 47
Real estate: Commercial and multifamily residential: Commercial land [Member]
Financing Receivable, Modifications, Number of Contracts | Modifications	1	0	0
Recorded Investment of Loans Collectively Measured for Contingency Provision	$ 293,694	$ 270,106
Recorded Investment of Loans Individually Measured for Specific Impairment	2,287	708
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Impaired Financing Receivable, Average Recorded Investment	2,079	425	$ 94
Impaired Financing Receivable, Interest Income, Accrual Method	$ 0	$ 0	$ 0
Real estate: Commercial and multifamiIy residential: Income property [Member]
Financing Receivable, Modifications, Number of Contracts | Modifications	1	0	0
Recorded Investment of Loans Collectively Measured for Contingency Provision	$ 1,901,313	$ 1,365,321
Recorded Investment of Loans Individually Measured for Specific Impairment	5,023	4,425
Recorded Investment	2,768	540
Unpaid Principal Balance	3,328	544
Related Allowance	185	27
Impaired Financing Receivable, Average Recorded Investment	4,314	2,492	$ 2,913
Impaired Financing Receivable, Interest Income, Accrual Method	$ 51	$ 26	$ 36
Real estate: Commercial and multifamiIy residential: Owner occupied [Member]
Financing Receivable, Modifications, Number of Contracts | Modifications	1	1	0
Recorded Investment of Loans Collectively Measured for Contingency Provision	$ 1,591,298	$ 1,054,564
Recorded Investment of Loans Individually Measured for Specific Impairment	8,688	5,414
Recorded Investment	77	0
Unpaid Principal Balance	80	0
Related Allowance	3	0
Impaired Financing Receivable, Average Recorded Investment	5,335	5,084	$ 7,052
Impaired Financing Receivable, Interest Income, Accrual Method	445	0	26
Real estate construction: One-to-four family residential: Land and acquisition [Member]
Recorded Investment of Loans Collectively Measured for Contingency Provision	9,907	11,542
Recorded Investment of Loans Individually Measured for Specific Impairment	0	14
Recorded Investment	0	14
Unpaid Principal Balance	0	102
Related Allowance	0	1
Impaired Financing Receivable, Average Recorded Investment	3	199	641
Impaired Financing Receivable, Interest Income, Accrual Method	0	0	5
Real estate construction: One-to-four family residential: Residential construction [Member]
Recorded Investment of Loans Collectively Measured for Contingency Provision	188,481	109,293
Recorded Investment of Loans Individually Measured for Specific Impairment	1,210	336
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Impaired Financing Receivable, Average Recorded Investment	309	472	648
Impaired Financing Receivable, Interest Income, Accrual Method	0	0	$ 0
Real estate construction: Commercial and multifamily residential: Income property [Member]
Recorded Investment of Loans Collectively Measured for Contingency Provision	293,028	103,779
Recorded Investment of Loans Individually Measured for Specific Impairment	0	0
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	$ 0	$ 0
Real estate construction: Commercial and multifamily residential: Owner occupied [Member]
Financing Receivable, Modifications, Number of Contracts | Modifications	1	0	0
Recorded Investment of Loans Collectively Measured for Contingency Provision	$ 68,393	$ 103,480
Recorded Investment of Loans Individually Measured for Specific Impairment	4,050	0
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Impaired Financing Receivable, Average Recorded Investment	1,620	0	$ 0
Impaired Financing Receivable, Interest Income, Accrual Method	$ 203	$ 0	$ 0
Consumer [Member]
Financing Receivable, Modifications, Number of Contracts | Modifications	42	41	1
Recorded Investment of Loans Collectively Measured for Contingency Provision	$ 325,210	$ 319,307
Recorded Investment of Loans Individually Measured for Specific Impairment	7,015	5,215
Impaired Financing Receivable, Average Recorded Investment	5,973	2,710	$ 189
Impaired Financing Receivable, Interest Income, Accrual Method	163	122	$ 4
Impaired Loans Without Recorded Allowance [Member]
Recorded Investment	56,357	17,592
Unpaid Principal Balance	64,735	27,228
Impaired Loans With Recorded Allowance [Member]
Recorded Investment	12,848	7,867
Unpaid Principal Balance	14,345	8,381
Related Allowance	2,360	761
Impaired Loans Without Recorded Allowance [Member]
Recorded Investment	1,712	751
Unpaid Principal Balance	1,864	833
Impaired Loans Without Recorded Allowance [Member] | Commercial business: Secured loans [Member]
Recorded Investment	36,204	6,404
Unpaid Principal Balance	42,314	12,831
Impaired Loans Without Recorded Allowance [Member] | Commercial business: Unsecured loans [Member]
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Impaired Loans Without Recorded Allowance [Member] | Real estate: One-to-four family residential [Member]
Recorded Investment	28	94
Unpaid Principal Balance	337	291
Impaired Loans Without Recorded Allowance [Member] | Real estate: Commercial and multifamily residential: Commercial land [Member]
Recorded Investment	2,287	708
Unpaid Principal Balance	2,282	687
Impaired Loans Without Recorded Allowance [Member] | Real estate: Commercial and multifamiIy residential: Income property [Member]
Recorded Investment	2,255	3,885
Unpaid Principal Balance	2,601	4,148
Impaired Loans Without Recorded Allowance [Member] | Real estate: Commercial and multifamiIy residential: Owner occupied [Member]
Recorded Investment	8,611	5,414
Unpaid Principal Balance	10,077	8,102
Impaired Loans Without Recorded Allowance [Member] | Real estate construction: One-to-four family residential: Land and acquisition [Member]
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Impaired Loans Without Recorded Allowance [Member] | Real estate construction: One-to-four family residential: Residential construction [Member]
Recorded Investment	1,210	336
Unpaid Principal Balance	1,210	336
Impaired Loans Without Recorded Allowance [Member] | Real estate construction: Commercial and multifamily residential: Income property [Member]
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Impaired Loans Without Recorded Allowance [Member] | Real estate construction: Commercial and multifamily residential: Owner occupied [Member]
Recorded Investment	4,050	0
Unpaid Principal Balance	$ 4,050	$ 0