FAIR VALUE MEASUREMENTS (Tables)

3 Months Ended

Mar. 31, 2016

Accounting Changes and Error Corrections [Abstract]

Schedule of assets measured at fair value on recurring basis

	As of March 31,  2016
	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	$	—	$	88,205	$	—	$	88,205
U.S. agency		—		16,242		—		16,242
Non-U.S. govt. & agency		—		6,779		—		6,779
Agency MBS		—		250,815		—		250,815
ABS/CMBS*		—		91,298		—		91,298
Corporate		—		559,989		—		559,989
Municipal		—		543,640		—		543,640
Equity		389,551		—		—		389,551
Total available-for-sale securities	$	389,551	$	1,556,968	$	—	$	1,946,519

	As of December 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	$	—	$	43,543	$	—	$	43,543
U.S. agency		—		15,740		—		15,740
Non-U.S. govt. & agency		—		4,478		—		4,478
Agency MBS		—		254,892		—		254,892
ABS/CMBS*		—		91,948		—		91,948
Corporate		—		517,109		—		517,109
Municipal		—		610,400		—		610,400
Equity		375,424		—		—		375,424
Total available-for-sale securities	$	375,424	$	1,538,110	$	—	$	1,913,534

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