Acquisitions - Schedule of Purchase Price Allocation (Details) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2017	Dec. 31, 2016
Business Acquisition
Reinsurance Payable	$ (241,768)	$ (99,891)
Prepaid reinsurance premiums	285,121	$ 132,564
Interboro Insurance Company
Business Acquisition
Cash and Cash Equivalents	15,554
Investments	66,527
Premium and Agents' Receivable	3,186
Goodwill	10,157
Intangible assets	5,877
Insurance contract asset	8,334
Deferred tax assets	575
Other assets	3,980
Loss Reserves	(24,967)
Unearned Premiums	26,243
Reinsurance Receivable	1,042
Other liabilities	(2,079)
Total purchase price	60,471
Advanced Premiums	(1,472)
AmCo Holding Company
Business Acquisition
Cash and Cash Equivalents	95,284
Investments	222,920
Premium and Agents' Receivable	31,439
Goodwill	46,109
Intangible assets	30,286
Insurance contract asset	33,812
Other assets	25,932
Loss Reserves	(60,529)
Unearned Premiums	128,824
Reinsurance Receivable	20,230
Deferred tax liabilities	(15,046)
Other liabilities	(27,367)
Total purchase price	274,384
Reinsurance Payable	(22,406)
Prepaid reinsurance premiums	$ 22,544

Business Combination, Assets Acquired and Liabilities Assumed, Loss Reserves

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Business Combination, Assets Acquired and Liabilities Assumed, Reinsurance Receivable

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Business Combination, Assets Acquired and Liabilities Assumed, Unearned Premiums

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Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

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Amount of currency on hand as well as demand deposits with banks or financial institutions, acquired at the acquisition date. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Amount of investments in debt and equity securities, including, but not limited to, held-to-maturity, trading and available-for-sale expected to be converted to cash, sold or exchanged within one year or the normal operating cycle, if longer, acquired at the acquisition date.

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Amount of other assets expected to be realized or consumed before one year or the normal operating cycle, if longer, acquired at the acquisition date.

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Amount due from customers or clients for goods or services, including trade receivables, that have been delivered or sold in the normal course of business, and amounts due from others, including related parties expected to be converted to cash, sold or exchanged within one year or the normal operating cycle, if longer, acquired at the acquisition date.

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Amount of deferred revenue expected to be recognized as such within one year or the normal operating cycle, if longer, assumed at the acquisition date.

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Amount of deferred tax asset attributable to deductible temporary differences and carryforwards acquired at the acquisition date.

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Amount of deferred tax liability attributable to taxable temporary differences assumed at the acquisition date.

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Amount of intangible assets, excluding goodwill, acquired at the acquisition date.

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The amount of identifiable intangible assets recognized as of the acquisition date.

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Amount of other liabilities due after one year or the normal operating cycle, if longer, assumed at the acquisition date.

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Amount recognized for assets, including goodwill, in excess of (less than) the aggregate liabilities assumed.

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The unexpired portion of premiums ceded on policies in force as of the balance sheet date.

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The carrying amount as of the balance sheet date of the known and estimated amounts owed to insurers under reinsurance treaties or other arrangements.

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