VARIABLE INTEREST ENTITIES, Not the Primary Beneficiary - Aggregate Assets, Liabilities Exposure to Loss (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Sep. 30, 2015
LIHTC funds - not primary beneficiary
Variable interest entity, nonconsolidated, carrying amount of assets and liabilities [Abstract]
Aggregate assets	$ 3,727,454	$ 3,317,594
Aggregate liabilities	1,114,185	951,465
Our risk of loss	73,959	42,244
NMTC funds - not primary beneficiary
Variable interest entity, nonconsolidated, carrying amount of assets and liabilities [Abstract]
Aggregate assets	65,468	65,388
Aggregate liabilities	67	40
Our risk of loss	12	12
Other real estate limited partnerships and LLCs - not primary beneficiary
Variable interest entity, nonconsolidated, carrying amount of assets and liabilities [Abstract]
Aggregate assets	29,523	29,523
Aggregate liabilities	37,062	37,062
Our risk of loss	140	163
Total VIEs - not primary beneficiary
Variable interest entity, nonconsolidated, carrying amount of assets and liabilities [Abstract]
Aggregate assets	3,822,445	3,412,505
Aggregate liabilities	1,151,314	988,567
Our risk of loss	$ 74,111	$ 42,419