Available-for-sale securities (Details) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2015	Sep. 30, 2014
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 7,906
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	1
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(74)
Available-for-sale Securities, Equity & Debt Maturities, Next Rolling Twelve Months, Fair Value	2,204
Available-for-sale Securities, Equity & Debt Maturities, Rolling Year One Through Three, Fair Value	4,122
Available-for-sale Securities, Equity & Debt Maturities, Rolling After Year Three, Fair Value	1,507
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis		$ 14,350
Available-for-sale Equity Securities, Accumulated Gross Unrealized Gain, before Tax		4,809
Available-for-sale Equity Securities, Accumulated Gross Unrealized Loss, before Tax		0
Available-for-sale Securities		$ 19,159
Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Equity Maturities, Next Rolling Twelve Months, Fair Value	1,751
Available-for-sale Securities, Amortized Cost Basis	1,750
Available-for-sale Equity Securities, Accumulated Gross Unrealized Gain, before Tax	1
Available-for-sale Equity Securities, Accumulated Gross Unrealized Loss, before Tax	0
Available-for-sale Securities	1,751
Available-for-sale Securities, Equity Maturities, Rolling Year One Through Three, Fair Value	0
Available-for-sale Securities, Equity Maturities, Rolling After Year Three, Fair Value	0
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	6,156
Available-for-sale Securities	6,082
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	0
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	(74)
Available-for-sale Securities, Debt Maturities, Next Rolling Twelve Months, Fair Value	453
Available-for-sale Securities, Debt Maturities, Rolling Year One Through Three, Fair Value	4,122
Available-for-sale Securities, Debt Maturities, Rolling After Year Three, Fair Value	1,507
Available-for-sale Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	0
Available-for-sale Securities	$ 7,833

Available-for-sale Securities, Debt Maturities, Rolling After Year Three, Fair Value

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Available-for-sale Securities, Debt Maturities, Rolling Year One Through Three, Fair Value

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Available-for-sale Securities, Equity & Debt Maturities, Next Rolling Twelve Months, Fair Value

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Available-for-sale Securities, Equity & Debt Maturities, Rolling After Year Three, Fair Value

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Available-for-sale Securities, Equity & Debt Maturities, Rolling Year One Through Three, Fair Value

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in equity securities classified as available-for-sale.

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Fair value of available-for-sale debt securities maturing in the next rolling twelve months following the latest balance sheet. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount after tax of reclassification adjustment from accumulated other comprehensive income for unrealized gain (loss) realized upon the sale of available-for-sale securities.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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