Regulatory Capital (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013
Sterling [Member]
Tier 1 leverage [Abstract]
Tier 1 leverage - actual	$ 1,124,391
Tier 1 leverage ratio - actual	12.20%
Tier 1 leverage - adequately capitalized	369,027
Tier 1 leverage ratio - adequately capitalized	4.00%
Tier 1 leverage - well capitalized	461,284
Tier 1 leverage ratio - well capitalized	5.00%
Tier 1 risk-based capital [Abstract]
Tier 1 risk-based capital - actual	1,124,391
Tier 1 risk-based capital ratio - actual	16.30%
Tier 1 risk-based capital - adequately capitalized	275,381
Tier 1 risk-based capital ratio - adequately capitalized	4.00%
Tier 1 risk-based capital - well capitalized	413,072
Tier 1 risk-based capital ratio - well capitalized	6.00%
Total risk-based capital [Abstract]
Total risk-based capital - actual	1,211,255
Total risk-based capital ratio - actual	17.60%
Total risk-based capital - adequately capitalized	550,763
Total risk-based capital ratio - adequately capitalized	8.00%
Total risk-based capital - well capitalized	688,453
Total risk-based capital ratio - well capitalized	10.00%
Sterling Bank [Member]
Tier 1 leverage [Abstract]
Tier 1 leverage - actual	1,104,601
Tier 1 leverage ratio - actual	12.00%
Tier 1 leverage - adequately capitalized	369,037
Tier 1 leverage ratio - adequately capitalized	4.00%
Tier 1 leverage - well capitalized	461,296
Tier 1 leverage ratio - well capitalized	5.00%
Tier 1 risk-based capital [Abstract]
Tier 1 risk-based capital - actual	1,104,601
Tier 1 risk-based capital ratio - actual	16.00%
Tier 1 risk-based capital - adequately capitalized	275,462
Tier 1 risk-based capital ratio - adequately capitalized	4.00%
Tier 1 risk-based capital - well capitalized	413,193
Tier 1 risk-based capital ratio - well capitalized	6.00%
Total risk-based capital [Abstract]
Total risk-based capital - actual	1,191,490
Total risk-based capital ratio - actual	17.30%
Total risk-based capital - adequately capitalized	550,924
Total risk-based capital ratio - adequately capitalized	8.00%
Total risk-based capital - well capitalized	$ 688,655
Total risk-based capital ratio - well capitalized	10.00%