FAIR VALUE, Significant Assumptions Used in Valuation of Level 3 Financial Instruments (Details) - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2016	Sep. 30, 2015
Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Total assets at fair value on a recurring basis	$ 2,277,240	$ 2,087,170
Nonrecurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Total assets at fair value on a nonrecurring basis	140,483	80,917
Significant unobservable inputs (level 3) | Recurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Total assets at fair value on a recurring basis	350,274	355,543
Significant unobservable inputs (level 3) | Recurring | ARS - municipal group one | Discounted cash flow
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Total assets at fair value on a recurring basis	$ 10,500
Significant unobservable inputs (level 3) | Recurring | ARS - municipal group one | Discounted cash flow | Minimum
Fair Value Inputs [Abstract]
Average discount rate	5.37%
Average interest rates applicable to future interest income on the securities	1.29%
Prepayment year	Dec. 31, 2018
Significant unobservable inputs (level 3) | Recurring | ARS - municipal group one | Discounted cash flow | Maximum
Fair Value Inputs [Abstract]
Average discount rate	6.61%
Average interest rates applicable to future interest income on the securities	2.31%
Prepayment year	Dec. 31, 2025
Significant unobservable inputs (level 3) | Recurring | ARS - municipal group one | Discounted cash flow | Weighted average
Fair Value Inputs [Abstract]
Average discount rate	5.99%
Average interest rates applicable to future interest income on the securities	1.80%
Prepayment year	Dec. 31, 2022
Significant unobservable inputs (level 3) | Recurring | ARS - municipals group two | Discounted cash flow
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Total assets at fair value on a recurring basis	$ 14,922
Significant unobservable inputs (level 3) | Recurring | ARS - municipals group two | Discounted cash flow | Minimum
Fair Value Inputs [Abstract]
Average discount rate	4.58%
Average interest rates applicable to future interest income on the securities	1.07%
Prepayment year	Dec. 31, 2016
Significant unobservable inputs (level 3) | Recurring | ARS - municipals group two | Discounted cash flow | Maximum
Fair Value Inputs [Abstract]
Average discount rate	5.58%
Average interest rates applicable to future interest income on the securities	1.07%
Prepayment year	Dec. 31, 2021
Significant unobservable inputs (level 3) | Recurring | ARS - municipals group two | Discounted cash flow | Weighted average
Fair Value Inputs [Abstract]
Average discount rate	5.08%
Average interest rates applicable to future interest income on the securities	1.07%
Prepayment year	Dec. 31, 2020
Significant unobservable inputs (level 3) | Recurring | ARS - preferred securities | Discounted cash flow
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Total assets at fair value on a recurring basis	$ 102,599
Significant unobservable inputs (level 3) | Recurring | ARS - preferred securities | Discounted cash flow | Minimum
Fair Value Inputs [Abstract]
Average discount rate	4.58%
Average interest rates applicable to future interest income on the securities	1.07%
Prepayment year	Dec. 31, 2016
Significant unobservable inputs (level 3) | Recurring | ARS - preferred securities | Discounted cash flow | Maximum
Fair Value Inputs [Abstract]
Average discount rate	6.38%
Average interest rates applicable to future interest income on the securities	2.83%
Prepayment year	Dec. 31, 2021
Significant unobservable inputs (level 3) | Recurring | ARS - preferred securities | Discounted cash flow | Weighted average
Fair Value Inputs [Abstract]
Average discount rate	5.50%
Average interest rates applicable to future interest income on the securities	1.50%
Prepayment year	Dec. 31, 2020
Significant unobservable inputs (level 3) | Recurring | Private equity investments | Income or market approach
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Total assets at fair value on a recurring basis	$ 49,393
Significant unobservable inputs (level 3) | Recurring | Private equity investments | Scenario 1 Income approach - discounted cash flow | Minimum
Fair Value Inputs [Abstract]
Discount rate	13.00%
Terminal growth rate of cash flows	3.00%
Terminal year	Dec. 31, 2017
Significant unobservable inputs (level 3) | Recurring | Private equity investments | Scenario 1 Income approach - discounted cash flow | Maximum
Fair Value Inputs [Abstract]
Discount rate	21.00%
Terminal growth rate of cash flows	3.00%
Terminal year	Dec. 31, 2019
Significant unobservable inputs (level 3) | Recurring | Private equity investments | Scenario 1 Income approach - discounted cash flow | Weighted average
Fair Value Inputs [Abstract]
Discount rate	17.80%
Terminal growth rate of cash flows	3.00%
Terminal year	Dec. 31, 2018
Significant unobservable inputs (level 3) | Recurring | Private equity investments | Scenario 2 - market approach - market multiple method | Minimum
Fair Value Inputs [Abstract]
Weighting assigned to outcome of scenario 1 / scenario 2	75.00%
EBITDA multiple	4.75
Significant unobservable inputs (level 3) | Recurring | Private equity investments | Scenario 2 - market approach - market multiple method | Maximum
Fair Value Inputs [Abstract]
Weighting assigned to outcome of scenario 1 / scenario 2	25.00%
EBITDA multiple	7.5
Significant unobservable inputs (level 3) | Recurring | Private equity investments | Scenario 2 - market approach - market multiple method | Weighted average
Fair Value Inputs [Abstract]
EBITDA multiple	6.1
Significant unobservable inputs (level 3) | Recurring | Private equity investments | Transaction price or other investment-specific events
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Total assets at fair value on a recurring basis	$ 155,005
Significant unobservable inputs (level 3) | Nonrecurring
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Total assets at fair value on a nonrecurring basis	35,720	$ 37,830
Significant unobservable inputs (level 3) | Nonrecurring | Impaired loans residential | Discounted cash flow
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Total assets at fair value on a nonrecurring basis	$ 22,937
Significant unobservable inputs (level 3) | Nonrecurring | Impaired loans residential | Discounted cash flow | Minimum
Fair Value Inputs [Abstract]
Prepayment rate (in years)	7 years
Significant unobservable inputs (level 3) | Nonrecurring | Impaired loans residential | Discounted cash flow | Maximum
Fair Value Inputs [Abstract]
Prepayment rate (in years)	12 years
Significant unobservable inputs (level 3) | Nonrecurring | Impaired loans residential | Discounted cash flow | Weighted average
Fair Value Inputs [Abstract]
Prepayment rate (in years)	10 years 2 months 15 days
Significant unobservable inputs (level 3) | Nonrecurring | Impaired loans corporate | Appraisal or discounts cash flow
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Total assets at fair value on a nonrecurring basis	$ 12,783