Loans and Allowance for Credit Losses (Schedule of Credit Exposure for Loans Based on Original LTV and FICO Score) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss and Fee	$ 23,834,889	$ 23,154,988
Residential and Other Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, before Allowance for Credit Loss and Fee	5,577,807	5,661,119
1-4 single family residential
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	255,615	820,613
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	820,369	615,021
Financing Receivable, Originated Two Years before Latest Fiscal Year	494,020	835,512
Financing Receivable, before Allowance for Credit Loss and Fee	4,743,866	4,953,936
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	1,633,100	1,245,630
Financing Receivable, Originated Four Years before Latest Fiscal Year	784,899	644,937
Financing Receivable, Originated Three Years before Latest Fiscal Year	755,863	792,223
FICO, 760 or greater | 1-4 single family residential
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	168,920	470,057
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	482,818	340,716
Financing Receivable, Originated Two Years before Latest Fiscal Year	298,650	534,017
Financing Receivable, before Allowance for Credit Loss and Fee	3,138,330	3,073,107
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	1,093,732	763,807
Financing Receivable, Originated Four Years before Latest Fiscal Year	573,011	430,706
Financing Receivable, Originated Three Years before Latest Fiscal Year	521,199	533,804
FICO, 720 to 759 | 1-4 single family residential
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	70,279	242,806
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	224,961	185,939
Financing Receivable, Originated Two Years before Latest Fiscal Year	112,407	200,623
Financing Receivable, before Allowance for Credit Loss and Fee	982,209	1,256,450
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	304,460	307,195
Financing Receivable, Originated Four Years before Latest Fiscal Year	131,205	141,748
Financing Receivable, Originated Three Years before Latest Fiscal Year	138,897	178,139
FICO, 719 or less | 1-4 single family residential
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	16,416	107,750
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	112,590	88,366
Financing Receivable, Originated Two Years before Latest Fiscal Year	82,963	100,872
Financing Receivable, before Allowance for Credit Loss and Fee	623,327	624,379
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	234,908	174,628
Financing Receivable, Originated Four Years before Latest Fiscal Year	80,683	72,483
Financing Receivable, Originated Three Years before Latest Fiscal Year	95,767	80,280
Less than 61% [Member] | 1-4 single family residential
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	99,728	171,069
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	180,025	134,978
Financing Receivable, Originated Two Years before Latest Fiscal Year	106,359	183,807
Financing Receivable, before Allowance for Credit Loss and Fee	1,383,912	1,287,982
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	519,410	372,221
Financing Receivable, Originated Four Years before Latest Fiscal Year	276,035	197,039
Financing Receivable, Originated Three Years before Latest Fiscal Year	202,355	228,868
61% - 70% [Member] | 1-4 single family residential
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	62,031	195,572
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	192,880	128,766
Financing Receivable, Originated Two Years before Latest Fiscal Year	110,546	152,502
Financing Receivable, before Allowance for Credit Loss and Fee	1,080,548	1,136,034
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	394,279	316,031
Financing Receivable, Originated Four Years before Latest Fiscal Year	184,600	154,307
Financing Receivable, Originated Three Years before Latest Fiscal Year	136,212	188,856
71% - 80% [Member] | 1-4 single family residential
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	92,387	442,311
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	433,542	313,779
Financing Receivable, Originated Two Years before Latest Fiscal Year	245,829	404,743
Financing Receivable, before Allowance for Credit Loss and Fee	2,111,127	2,313,412
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	689,223	531,377
Financing Receivable, Originated Four Years before Latest Fiscal Year	300,153	283,202
Financing Receivable, Originated Three Years before Latest Fiscal Year	349,993	338,000
More than 81% [Member] | 1-4 single family residential
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	1,469	11,661
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	13,922	37,498
Financing Receivable, Originated Two Years before Latest Fiscal Year	31,286	94,460
Financing Receivable, before Allowance for Credit Loss and Fee	168,279	216,508
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	30,188	26,001
Financing Receivable, Originated Four Years before Latest Fiscal Year	24,111	10,389
Financing Receivable, Originated Three Years before Latest Fiscal Year	$ 67,303	$ 36,499