DEBT AND OTHER OBLIGATIONS (Details) (USD $)	6 Months Ended			0 Months Ended	6 Months Ended				6 Months Ended	12 Months Ended	6 Months Ended			0 Months Ended																		0 Months Ended	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Oct. 10, 2012 Golden Gate V and Red Mountain	Jun. 30, 2013 Golden Gate II Captive Insurance Company	Jun. 30, 2013 Golden Gate V Vermont Captive Insurance Company	Jun. 30, 2013 Red Mountain	Oct. 10, 2012 Red Mountain	Jun. 30, 2013 Repurchase Program Borrowings	Dec. 31, 2012 Repurchase Program Borrowings	Jun. 30, 2013 Repurchase Program Borrowings Maximum	Jun. 30, 2013 Revolving Line of Credit	Dec. 31, 2012 Revolving Line of Credit	Jun. 03, 2013 4.30% Senior Notes (2003), due 2013	Dec. 31, 2012 4.30% Senior Notes (2003), due 2013	Jun. 30, 2013 4.875% Senior Notes (2004), due 2014	Dec. 31, 2012 4.875% Senior Notes (2004), due 2014	Jun. 30, 2013 6.40% Senior Notes (2007), due 2018	Dec. 31, 2012 6.40% Senior Notes (2007), due 2018	Jun. 30, 2013 7.375% Senior Notes (2009), due 2019	Dec. 31, 2012 7.375% Senior Notes (2009), due 2019	Jun. 30, 2013 8.00% Senior Notes (2009), due 2024, callable 2014	Dec. 31, 2012 8.00% Senior Notes (2009), due 2024, callable 2014	Jun. 30, 2013 8.45% Senior Notes (2009), due 2039	Dec. 31, 2012 8.45% Senior Notes (2009), due 2039	Jun. 30, 2013 6.125% Subordinated Debentures (2004), due 2034, callable 2009	Dec. 31, 2012 6.125% Subordinated Debentures (2004), due 2034, callable 2009	Jun. 30, 2013 6.25% Subordinated Debentures (2012) due 2042, callable 2017	Dec. 31, 2012 6.25% Subordinated Debentures (2012) due 2042, callable 2017	Jun. 30, 2013 6.00% Subordinated Debentures (2012) due 2042, callable 2017	Dec. 31, 2012 6.00% Subordinated Debentures (2012) due 2042, callable 2017	Jun. 03, 2013 Credit Facility	Jun. 30, 2013 Credit Facility	Jun. 30, 2013 Credit Facility Federal Funds Rate	Jun. 30, 2013 Credit Facility LIBOR One-Month Rate
Debt and other obligations
Stated interest rate (as a percent)															4.30%	4.875%	4.875%	6.40%	6.40%	7.375%	7.375%	8.00%	8.00%	8.45%	8.45%	6.125%	6.125%	6.25%	6.25%	6.00%	6.00%
Total debt	$ 1,460,000,000		$ 1,400,000,000									$ 360,000,000	$ 50,000,000		$ 250,000,000	$ 150,000,000	$ 150,000,000	$ 150,000,000	$ 150,000,000	$ 400,000,000	$ 400,000,000	$ 100,000,000	$ 100,000,000	$ 300,000,000	$ 300,000,000
Total subordinated debt securities	540,593,000		540,593,000																							103,093,000	103,093,000	287,500,000	287,500,000	150,000,000	150,000,000
Line of credit, current borrowing capacity																																	750,000,000
Line of credit, maximum borrowing capacity to be granted upon entity's request																																	1,000,000,000
Base of floating rate interest rate payments																																	LIBOR	Federal Funds rate	one-month LIBOR
Interest rate added to the base rate (as a percent)																																	1.20%	0.50%	1.00%
Line of credit, amount outstanding																																	360,000,000
Repayment of debt														250,000,000
Borrowing of additional line of credit																																250,000,000
Outstanding non-recourse funding obligations of Golden Gate II Captive Insurance Company	575,000,000
Term of transaction				20 years
Maximum financing capacity under transaction				945,000,000				945,000,000
Principal amount of note issued							335,000,000	275,000,000
Non-recourse funding obligations	604,900,000		586,000,000		269,900,000	335,000,000
Non-recourse funding obligations held by affiliates	305,100,000
Year-to-date weighted-average interest rate of non-recourse funding obligations (as a percent)					1.00%	6.25%
Outstanding nonrecourse funding obligations repurchased at discount	16,100,000	110,800,000
Gain from repurchase of outstanding nonrecourse funding obligations	3,400,000	35,500,000
Fair value of securities pledged under the repurchase program									356,100,000
Repurchase program borrowings	340,000,000		150,000,000						340,000,000
Average borrowing rate (as a percent)									0.08%
Maximum balance outstanding									645,100,000	425,000,000
Average daily balance									423,900,000	266,300,000
Average borrowing rate (as a percent)									0.12%	0.14%
Outstanding balance										$ 150,000,000
Term of debt											90 days