FAIR VALUE MEASUREMENTS (Tables)

9 Months Ended

Sep. 30, 2015

Accounting Changes and Error Corrections [Abstract]

Schedule of assets measured at fair value on recurring basis

	As of September 30,  2015
	Fair Value Measurements Using
	Quoted Prices in		Significant Other		Significant
	Active Markets for		Observable		Unobservable
	Identical Assets		Inputs		Inputs
(in thousands)	(Level 1)		(Level 2)		(Level 3)		Total
Available-for-sale securities
U.S. government	$	—	$	33,036	$	—	$	33,036
U.S. agency		—		13,867		—		13,867
Non-U.S. govt. & agency		—		4,664		—		4,664
Agency MBS		—		261,272		—		261,272
ABS/CMBS*		—		84,809		—		84,809
Corporate		—		602,023		—		602,023
Municipal		—		532,633		—		532,633
Equity		369,047		—		—		369,047
Total available-for-sale securities	$	369,047	$	1,532,304	$	—	$	1,901,351

*Non-agency asset-backed and commercial mortgage-backed

	As of December 31,  2014
	Fair Value Measurements Using
	Quoted Prices in		Significant Other		Significant
	Active Markets for		Observable		Unobservable
	Identical Assets		Inputs		Inputs
(in thousands)	(Level 1)		(Level 2)		(Level 3)		Total
Available-for-sale securities
U.S. government	$	—	$	33,788	$	—	$	33,788
U.S. agency		—		6,747		—		6,747
Non-U.S. govt. & agency		—		10,665		—		10,665
Agency MBS		—		264,468		—		264,468
ABS/CMBS*		—		135,304		—		135,304
Corporate		—		562,690		—		562,690
Municipal		—		481,425		—		481,425
Equity		410,642		—		—		410,642
Total available-for-sale securities	$	410,642	$	1,495,087	$	—	$	1,905,729

* Non-agency asset-backed and commercial mortgage-backed