FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Liabilities:
Senior notes	$ 490,753	$ 123,008
Junior subordinated notes	234,979	250,154
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash, restricted cash, and cash equivalents	1,253,809	1,139,549
Liabilities:
Senior notes	117,576	116,699
Junior subordinated notes	0	0
Significant Other Observable Inputs (Level 2)
Assets:
Cash, restricted cash, and cash equivalents	0	0
Liabilities:
Senior notes	0	0
Junior subordinated notes	0	0
Significant Unobservable Inputs (Level 3)
Assets:
Cash, restricted cash, and cash equivalents	0	0
Liabilities:
Senior notes	367,845	0
Junior subordinated notes	200,793	210,084
Carrying Amount
Assets:
Cash, restricted cash, and cash equivalents	1,253,809	1,139,549
Liabilities:
Senior notes	490,753	123,008
Junior subordinated notes	234,979	250,154
Estimated Fair Value
Assets:
Cash, restricted cash, and cash equivalents	1,253,809	1,139,549
Liabilities:
Senior notes	485,421	116,699
Junior subordinated notes	$ 200,793	$ 210,084