Fair value measurements (Tables)

12 Months Ended

Dec. 31, 2015

Fair Value Disclosures [Abstract]

Financial Instruments Measured at Fair Value on Recurring Basis

At December 31, 2015, financial instruments measured at fair value on a recurring basis are summarized below:

	Level 1	Level 2	Level 3	Fair value measurements
	($000 omitted)
Investments available-for-sale:
Debt securities:
Municipal	—	72,008	—	72,008
Corporate	—	309,461	—	309,461
Foreign	—	153,221	—	153,221
U.S. Treasury Bonds	—	13,906	—	13,906
Equity securities:	31,253	—	—	31,253
	31,253	548,596	—	579,849

At December 31, 2014, financial instruments measured at fair value on a recurring basis are summarized below:

	Level 1	Level 2	Level 3	Fair value measurements
	($000 omitted)
Investments available-for-sale:
Debt securities:
Municipal	—	61,689	—	61,689
Corporate	—	308,691	—	308,691
Foreign	—	166,685	—	166,685
U.S. Treasury Bonds	—	14,802	—	14,802
Equity securities:	28,236	—	—	28,236
	28,236	551,867	—	580,103

Assets Measured at Fair Value on Nonrecurring Basis

As of December 31, 2015 and 2014, assets measured at fair value on a nonrecurring basis are summarized below:

	2015		2014
	Level 3	Impairment loss recorded	Level 3	Impairment loss recorded
	($000 omitted)
Cost-basis investments	3,127	600	3,938	1,000