Regulatory Capital (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013
Sterling [Member]
Tier 1 leverage [Abstract]
Tier 1 leverage - actual	$ 1,134,493
Tier 1 leverage ratio - actual	11.80%
Tier 1 leverage - adequately capitalized	384,630
Tier 1 leverage ratio - adequately capitalized	4.00%
Tier 1 leverage - well capitalized	480,787
Tier 1 leverage ratio - well capitalized	5.00%
Tier 1 risk-based capital [Abstract]
Tier 1 risk-based capital - actual	1,134,493
Tier 1 risk-based capital ratio - actual	15.40%
Tier 1 risk-based capital - adequately capitalized	294,609
Tier 1 risk-based capital ratio - adequately capitalized	4.00%
Tier 1 risk-based capital - well capitalized	441,914
Tier 1 risk-based capital ratio - well capitalized	6.00%
Total risk-based capital [Abstract]
Total risk-based capital - actual	1,227,264
Total risk-based capital ratio - actual	16.70%
Total risk-based capital - adequately capitalized	589,219
Total risk-based capital ratio - adequately capitalized	8.00%
Total risk-based capital - well capitalized	736,523
Total risk-based capital ratio - well capitalized	10.00%
Sterling Bank [Member]
Tier 1 leverage [Abstract]
Tier 1 leverage - actual	1,111,164
Tier 1 leverage ratio - actual	11.60%
Tier 1 leverage - adequately capitalized	384,647
Tier 1 leverage ratio - adequately capitalized	4.00%
Tier 1 leverage - well capitalized	480,809
Tier 1 leverage ratio - well capitalized	5.00%
Tier 1 risk-based capital [Abstract]
Tier 1 risk-based capital - actual	1,111,164
Tier 1 risk-based capital ratio - actual	15.10%
Tier 1 risk-based capital - adequately capitalized	294,691
Tier 1 risk-based capital ratio - adequately capitalized	4.00%
Tier 1 risk-based capital - well capitalized	442,036
Tier 1 risk-based capital ratio - well capitalized	6.00%
Total risk-based capital [Abstract]
Total risk-based capital - actual	1,204,091
Total risk-based capital ratio - actual	16.30%
Total risk-based capital - adequately capitalized	589,381
Total risk-based capital ratio - adequately capitalized	8.00%
Total risk-based capital - well capitalized	$ 736,727
Total risk-based capital ratio - well capitalized	10.00%