Available-for-sale securities (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 7,969	$ 0
Available-for-sale Securities	7,890
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	4
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(83)
Available-for-sale Securities, Equity & Debt Maturities, Next Rolling Twelve Months, Fair Value	1,754
Available-for-sale Securities, Equity & Debt Maturities, Rolling Year One Through Three, Fair Value	4,883
Available-for-sale Securities, Equity & Debt Maturities, Rolling After Year Three, Fair Value	1,253
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Equity Maturities, Next Rolling Twelve Months, Fair Value	750
Available-for-sale Securities, Amortized Cost Basis	1,000
Available-for-sale Equity Securities, Accumulated Gross Unrealized Gain, before Tax	4
Available-for-sale Equity Securities, Accumulated Gross Unrealized Loss, before Tax	0
Available-for-sale Securities	1,004
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	254
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	6,969
Available-for-sale Securities	6,886
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	0
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	(83)
Available-for-sale Securities, Debt Maturities, Next Rolling Twelve Months, Fair Value	1,004
Available-for-sale Securities, Debt Maturities, Rolling Year One Through Three, Fair Value	4,883
Available-for-sale Securities, Debt Maturities, Rolling After Year Three, Fair Value	999
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, 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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Available-for-sale Securities, Equity Maturities, Next Rolling Twelve Months, 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 before tax of unrealized loss 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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