FAIR VALUE MEASUREMENTS (Tables)

3 Months Ended

Mar. 31, 2015

Accounting Changes and Error Corrections [Abstract]

Schedule of assets measured at fair value on recurring basis

	As of March 31,  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	$	—	$	33,592	$	—	$	33,592
U.S. agency		—		14,052		—		14,052
Non-U.S. govt. & agency		—		2,017		—		2,017
Agency MBS		—		254,314		—		254,314
ABS/CMBS*		—		127,922		—		127,922
Corporate		—		616,062		—		616,062
Municipal		—		481,600		—		481,600
Equity		391,663		—		—		391,663
Total available-for-sale securities	$	391,663	$	1,529,559	$	—	$	1,921,222

*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