Stockholders' Equity and Regulatory Capital - Schedule of Capital Position (Details) $ in Thousands	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Capital Unit [Line Items]
Total Capital (to risk-weighted assets), Consolidated Capital Amount	$ 1,610,964	$ 1,415,780
Tier 1 Capital (to risk-weighted assets), Consolidated Capital Amount	1,528,398	1,286,150
Common Equity Tier 1 Capital (to risk-weighted assets), Consolidated Bank Capital Amount	1,463,398	1,221,150
Tier 1 Capital (to adjusted tangible assets), Consolidated Capital Amount	$ 1,528,398	$ 1,286,150
Total Capital (to risk-weighted assets), Consolidated Capital Percent	0.1559	0.1376
Tier 1 Capital (to risk-weighted assets), Consolidated Capital Percent	0.1479	0.1250
Common Equity Tier 1 Capital (to risk-weighted assets), Consolidated Capital Percent	14.16%	11.87%
Tier 1 Leverage Capital , Consolidated Capital Percent	0.1024	0.0976
Total Capital (to risk-weighted assets), Minimum For Capital Adequacy Purposes Amount	$ 826,839	$ 823,355
Tier 1 Capital (to risk-weighted assets), Minimum For Capital Adequacy Purposes Amount	620,129	617,517
Common Equity Tier 1 Capital (to risk-weighted assets), Minimum For Capital Adequacy Purposes Amount	465,097	463,137
Tier 1 Leverage Capital, Minimum For Capital Adequacy Purposes Amount	$ 597,179	$ 527,192
Total Capital (to risk-weighted assets), Minimum For Capital Adequacy Purposes Percentage	0.0800	0.0800
Tier 1 Capital (to risk-weighted assets), Minimum For Capital Adequacy Purposes Percentage	0.0600	0.0600
Common Equity Tier 1 Capital (to risk-weighted assets), Minimum For Capital Adequacy Purposes Percentage	4.50%	4.50%
Tier 1 Leverage Capital, Minimum For Capital Adequacy Purposes Percentage	0.0400	0.0400
Total Capital (to risk-weighted assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions Amount	$ 1,033,548	$ 1,029,194
Tier 1 Capital (to risk-weighted assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions Amount	826,839	823,355
Common Equity Tier 1 Capital (to risk-weighted assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions Amount	671,806	668,976
Tier 1 Leverage Capital, To Be Well-Capitalized Under Prompt Corrective Action Provisions Amount	$ 746,473	$ 658,990
Total Capital (to risk-weighted assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions Percentage	0.1000	0.1000
Tier 1 Capital (to risk-weighted assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions Percentage	0.0800	0.0800
Common Equity Tier 1 Capital (to risk-weighted assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions Percentage	6.50%	6.50%
Tier 1 Leverage Capital, To Be Well-Capitalized Under Prompt Corrective Action Provisions Percentage	0.0500	0.0500
Wilmington Savings Fund Society, FSB
Capital Unit [Line Items]
Total Capital (to risk-weighted assets), Consolidated Capital Amount	$ 1,639,708	$ 1,412,290
Tier 1 Capital (to risk-weighted assets), Consolidated Capital Amount	1,557,142	1,283,022
Common Equity Tier 1 Capital (to risk-weighted assets), Consolidated Bank Capital Amount	1,557,142	1,283,022
Tier 1 Capital (to adjusted tangible assets), Consolidated Capital Amount	$ 1,557,142	$ 1,283,022
Total Capital (to risk-weighted assets), Consolidated Capital Percent	0.1591	0.1376
Tier 1 Capital (to risk-weighted assets), Consolidated Capital Percent	0.1511	0.1250
Common Equity Tier 1 Capital (to risk-weighted assets), Consolidated Capital Percent	15.11%	12.50%
Tier 1 Leverage Capital , Consolidated Capital Percent	0.1044	0.0974
Total Capital (to risk-weighted assets), Minimum For Capital Adequacy Purposes Amount	$ 824,687	$ 821,012
Tier 1 Capital (to risk-weighted assets), Minimum For Capital Adequacy Purposes Amount	618,515	615,759
Common Equity Tier 1 Capital (to risk-weighted assets), Minimum For Capital Adequacy Purposes Amount	463,886	461,819
Tier 1 Leverage Capital, Minimum For Capital Adequacy Purposes Amount	$ 596,711	$ 526,803
Total Capital (to risk-weighted assets), Minimum For Capital Adequacy Purposes Percentage	0.0800	0.0800
Tier 1 Capital (to risk-weighted assets), Minimum For Capital Adequacy Purposes Percentage	0.0600	0.0600
Common Equity Tier 1 Capital (to risk-weighted assets), Minimum For Capital Adequacy Purposes Percentage	4.50%	4.50%
Tier 1 Leverage Capital, Minimum For Capital Adequacy Purposes Percentage	0.0400	0.0400
Total Capital (to risk-weighted assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions Amount	$ 1,030,858	$ 1,026,265
Tier 1 Capital (to risk-weighted assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions Amount	824,687	821,012
Common Equity Tier 1 Capital (to risk-weighted assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions Amount	670,058	667,073
Tier 1 Leverage Capital, To Be Well-Capitalized Under Prompt Corrective Action Provisions Amount	$ 745,889	$ 658,503
Total Capital (to risk-weighted assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions Percentage	0.1000	0.1000
Tier 1 Capital (to risk-weighted assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions Percentage	0.0800	0.0800
Common Equity Tier 1 Capital (to risk-weighted assets), To Be Well-Capitalized Under Prompt Corrective Action Provisions Percentage	6.50%	6.50%
Tier 1 Leverage Capital, To Be Well-Capitalized Under Prompt Corrective Action Provisions Percentage	0.0500	0.0500