DEBT AND OTHER OBLIGATIONS - Summary of Debt and Subordinated Debt Securities (Details) - USD ($)	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2012	Oct. 09, 2009	Dec. 31, 2007
6.40% Senior Notes (2007), due 2018
Debt Instrument [Line Items]
Stated interest rate (as a percent)					6.40%
7.375% Senior Notes (2009), due 2019
Debt Instrument [Line Items]
Stated interest rate (as a percent)				7.375%
8.45% Senior Notes (2009), due 2039
Debt Instrument [Line Items]
Total debt				$ 300,000,000
Stated interest rate (as a percent)				8.45%
6.25% Subordinated Debentures (2012), due 2042, callable 2017
Debt Instrument [Line Items]
Stated interest rate (as a percent)			6.25%
6.00% Subordinated Debentures (2012), due 2042, callable 2017
Debt Instrument [Line Items]
Stated interest rate (as a percent)			6.00%
Successor
Debt Instrument [Line Items]
Outstanding Principal	$ 966,926,000	$ 1,335,000,000
Total debt	1,163,285,000	1,588,806,000
Total subordinated debt securities	441,202,000	448,763,000
Successor | 6.40% Senior Notes (2007), due 2018
Debt Instrument [Line Items]
Outstanding Principal	150,000,000	150,000,000
Total debt	$ 156,663,000	162,671,000
Stated interest rate (as a percent)	6.40%
Successor | 7.375% Senior Notes (2009), due 2019
Debt Instrument [Line Items]
Outstanding Principal	$ 400,000,000	400,000,000
Total debt	$ 454,688,000	473,127,000
Stated interest rate (as a percent)	7.375%
Successor | 8.45% Senior Notes (2009), due 2039
Debt Instrument [Line Items]
Outstanding Principal	$ 246,926,000	300,000,000
Total debt	$ 381,934,000	468,008,000
Stated interest rate (as a percent)	8.45%
Successor | 6.25% Subordinated Debentures (2012), due 2042, callable 2017
Debt Instrument [Line Items]
Total subordinated debt securities	$ 290,002,000	295,833,000
Stated interest rate (as a percent)	6.25%
Successor | 6.00% Subordinated Debentures (2012), due 2042, callable 2017
Debt Instrument [Line Items]
Total subordinated debt securities	$ 151,200,000	152,930,000
Stated interest rate (as a percent)	6.00%
Successor | Revolving Line Of Credit
Debt Instrument [Line Items]
Outstanding Principal	$ 170,000,000	485,000,000
Total debt	170,000,000	485,000,000
Successor | Subordinated debentures
Debt Instrument [Line Items]
Outstanding Principal	437,500,000	437,500,000
Successor | Subordinated debentures | 6.25% Subordinated Debentures (2012), due 2042, callable 2017
Debt Instrument [Line Items]
Outstanding Principal	287,500,000	287,500,000
Successor | Subordinated debentures | 6.00% Subordinated Debentures (2012), due 2042, callable 2017
Debt Instrument [Line Items]
Outstanding Principal	$ 150,000,000	$ 150,000,000