INVESTMENT BORROWINGS (DETAILS) (USD $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Investment borrowings	$ 1,850,200,000		$ 1,650,800,000
Interest rate	7.00%
Federal Home Loan Bank Advances [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Carrying value of FHLB common stock	92,500,000
Investment borrowings	1,849,700,000		1,700,000,000
Estimated fair value of collateralized investments for FHLB borrowings	2,300,000,000
Interest expense on FHLB borrowings	20,800,000	21,300,000
Aggregate fee to prepay all fixed rate FHLB borrowings	48,800,000
Repurchase Agreements [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Assets sold under agreements to repurchase	0
Other Borrowings [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Investment borrowings	500,000		800,000
Borrowings Due February 2014 [Member] | Federal Home Loan Bank Advances [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Investment borrowings	67,000,000
Maturity date	Feb. 28, 2014
Interest rate	1.83%
Borrowings Due September 2015 [Member] | Federal Home Loan Bank Advances [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Investment borrowings	50,000,000
Maturity date	Sep. 30, 2015
Interest rate	0.564%
Borrowings Due October 2015 [Member] | Federal Home Loan Bank Advances [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Investment borrowings	150,000,000
Maturity date	Oct. 31, 2015
Interest rate	0.532%
Borrowings Due November 2015 Rate One [Member] | Federal Home Loan Bank Advances [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Investment borrowings	100,000,000
Maturity date	Nov. 30, 2015
Interest rate	0.343%
Borrowings Due November 2015 Rate Two [Member] | Federal Home Loan Bank Advances [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Investment borrowings	146,000,000
Maturity date	Nov. 30, 2015
Interest rate	5.30%
Borrowings Due December 2015 [Member] | Federal Home Loan Bank Advances [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Investment borrowings	100,000,000
Maturity date	Dec. 31, 2015
Interest rate	4.71%
Borrowings Due June 2016 [Member] | Federal Home Loan Bank Advances [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Investment borrowings	100,000,000
Maturity date	Jun. 30, 2016
Interest rate	0.619%
Borrowings Due June 2016 Rate Two [Member] | Federal Home Loan Bank Advances [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Investment borrowings	75,000,000
Maturity date	Jun. 30, 2016
Interest rate	0.408%
Borrowings Due October 2016 [Member] | Federal Home Loan Bank Advances [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Investment borrowings	100,000,000
Maturity date	Oct. 31, 2016
Interest rate	0.426%
Borrowings Due November 2016 [Member] | Federal Home Loan Bank Advances [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Investment borrowings	50,000,000
Maturity date	Nov. 30, 2016
Interest rate	0.53%
Borrowings Due November 2016 Rate Two [Member] | Federal Home Loan Bank Advances [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Investment borrowings	50,000,000
Maturity date	Nov. 30, 2016
Interest rate	0.65%
Borrowings Due June 2017 [Member] | Federal Home Loan Bank Advances [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Investment borrowings	57,700,000
Maturity date	Jun. 30, 2017
Interest rate	0.612%
Borrowings Due July 2017 [Member] | Federal Home Loan Bank Advances [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Investment borrowings	100,000,000
Maturity date	Jul. 31, 2017
Interest rate	3.90%
Borrowings Due August 2017 [Member] | Federal Home Loan Bank Advances [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Investment borrowings	50,000,000
Maturity date	Aug. 31, 2017
Interest rate	0.464%
Borrowings Due August 2017 Rate 2 [Member] | Federal Home Loan Bank Advances [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Investment borrowings	75,000,000
Maturity date	Aug. 31, 2017
Interest rate	0.412%
Borrowings Due October 2017 [Member] | Federal Home Loan Bank Advances [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Investment borrowings	100,000,000
Maturity date	Oct. 31, 2017
Interest rate	0.698%
Borrowings Due November 2017 [Member] | Federal Home Loan Bank Advances [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Investment borrowings	37,000,000
Maturity date	Nov. 30, 2017
Interest rate	3.75%
Borrowings Due January 2018 Rate One [Member] | Federal Home Loan Bank Advances [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Investment borrowings	50,000,000
Maturity date	Jan. 31, 2018
Interest rate	0.619%
Borrowings Due January 2018 Rate Two [Member] | Federal Home Loan Bank Advances [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Investment borrowings	50,000,000
Maturity date	Jan. 31, 2018
Interest rate	0.605%
Borrowings Due February 2018 Rate One [Member] | Federal Home Loan Bank Advances [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Investment borrowings	50,000,000
Maturity date	Feb. 28, 2018
Interest rate	0.575%
Borrowings Due February 2018 Rate Two [Member] | Federal Home Loan Bank Advances [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Investment borrowings	22,000,000
Maturity date	Feb. 28, 2018
Interest rate	0.592%
Borrowings Due May 2018 [Member] | Federal Home Loan Bank Advances [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Investment borrowings	100,000,000
Maturity date	May 31, 2018
Interest rate	0.629%
Borrowings Due July 2018 [Member] | Federal Home Loan Bank Advances [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Investment borrowings	50,000,000
Maturity date	Jul. 31, 2018
Interest rate	0.734%
Borrowings Due August 2018 [Member] | Federal Home Loan Bank Advances [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Investment borrowings	50,000,000
Maturity date	Aug. 31, 2018
Interest rate	0.384%
Borrowings Due June 2020 [Member] | Federal Home Loan Bank Advances [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Investment borrowings	21,800,000
Maturity date	Jun. 30, 2020
Interest rate	1.96%
Borrowings Due March 2023 [Member] | Federal Home Loan Bank Advances [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Investment borrowings	27,700,000
Maturity date	Mar. 31, 2023
Interest rate	2.16%
Borrowings Due June 2025 [Member] | Federal Home Loan Bank Advances [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Investment borrowings	$ 20,500,000
Maturity date	Jun. 30, 2025
Interest rate	2.94%