Regulatory Capital (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012
Sterling [Member]
Tier One Leverage Capital [Abstract]
Tier One Leverage Capital	$ 1,136,913
Tier One Leverage Capital to Average Assets	12.70%
Tier One Leverage Capital Required for Capital Adequacy	358,636
Tier One Leverage Capital Required for Capital Adequacy to Average Assets	4.00%
Tier One Leverage Capital Required to be Well Capitalized	448,295
Tier One Leverage Capital Required to be Well Capitalized to Average Assets	5.00%
Tier One Risk Based Capital [Abstract]
Tier One Risk Based Capital	1,136,913
Tier One Risk Based Capital to Risk Weighted Assets	17.60%
Tier One Risk Based Capital Required for Capital Adequacy	258,113
Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	4.00%
Tier One Risk Based Capital Required to be Well Capitalized	387,169
Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	6.00%
Capital [Abstract]
Capital	1,218,578
Capital to Risk Weighted Assets	18.90%
Capital Required for Capital Adequacy	516,226
Capital Required for Capital Adequacy to Risk Weighted Assets	8.00%
Capital Required to be Well Capitalized	645,282
Capital Required to be Well Capitalized to Risk Weighted Assets	10.00%
Sterling Bank [Member]
Tier One Leverage Capital [Abstract]
Tier One Leverage Capital	1,131,674
Tier One Leverage Capital to Average Assets	12.60%
Tier One Leverage Capital Required for Capital Adequacy	360,756
Tier One Leverage Capital Required for Capital Adequacy to Average Assets	4.00%
Tier One Leverage Capital Required to be Well Capitalized	450,945
Tier One Leverage Capital Required to be Well Capitalized to Average Assets	5.00%
Tier One Risk Based Capital [Abstract]
Tier One Risk Based Capital	1,131,674
Tier One Risk Based Capital to Risk Weighted Assets	17.50%
Tier One Risk Based Capital Required for Capital Adequacy	258,372
Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	4.00%
Tier One Risk Based Capital Required to be Well Capitalized	387,559
Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	6.00%
Capital [Abstract]
Capital	1,213,419
Capital to Risk Weighted Assets	18.80%
Capital Required for Capital Adequacy	516,745
Capital Required for Capital Adequacy to Risk Weighted Assets	8.00%
Capital Required to be Well Capitalized	$ 645,931
Capital Required to be Well Capitalized to Risk Weighted Assets	10.00%