Regulatory Capital (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013
Sterling [Member]
Tier 1 leverage [Abstract]
Tier 1 leverage - actual	$ 1,142,864
Tier 1 leverage ratio - actual	12.80%
Tier 1 leverage - adequately capitalized	357,358
Tier 1 leverage ratio - adequately capitalized	4.00%
Tier 1 leverage - well capitalized	446,698
Tier 1 leverage ratio - well capitalized	5.00%
Tier 1 risk-based capital [Abstract]
Tier 1 risk-based capital - actual	1,142,864
Tier 1 risk-based capital ratio - actual	17.80%
Tier 1 risk-based capital - adequately capitalized	257,657
Tier 1 risk-based capital ratio - adequately capitalized	4.00%
Tier 1 risk-based capital - well capitalized	386,486
Tier 1 risk-based capital ratio - well capitalized	6.00%
Total risk-based capital [Abstract]
Total risk-based capital - actual	1,224,334
Total risk-based capital ratio - actual	19.00%
Total risk-based capital - adequately capitalized	515,315
Total risk-based capital ratio - adequately capitalized	8.00%
Total risk-based capital - well capitalized	644,143
Total risk-based capital ratio - well capitalized	10.00%
Sterling Bank [Member]
Tier 1 leverage [Abstract]
Tier 1 leverage - actual	1,129,888
Tier 1 leverage ratio - actual	12.60%
Tier 1 leverage - adequately capitalized	357,628
Tier 1 leverage ratio - adequately capitalized	4.00%
Tier 1 leverage - well capitalized	447,035
Tier 1 leverage ratio - well capitalized	5.00%
Tier 1 risk-based capital [Abstract]
Tier 1 risk-based capital - actual	1,129,888
Tier 1 risk-based capital ratio - actual	17.50%
Tier 1 risk-based capital - adequately capitalized	257,737
Tier 1 risk-based capital ratio - adequately capitalized	4.00%
Tier 1 risk-based capital - well capitalized	386,606
Tier 1 risk-based capital ratio - well capitalized	6.00%
Total risk-based capital [Abstract]
Total risk-based capital - actual	1,211,383
Total risk-based capital ratio - actual	18.80%
Total risk-based capital - adequately capitalized	515,474
Total risk-based capital ratio - adequately capitalized	8.00%
Total risk-based capital - well capitalized	$ 644,343
Total risk-based capital ratio - well capitalized	10.00%