5.	Workers' Compensation Claims

The following table summarizes the aggregate workers' compensation reserve activity (in thousands):

	Year Ended December 31,
	2016			2015			2014
Balance at January 1,
Workers' compensation claims liabilities	$	255,675		$	225,278		$	121,056
Add: claims expense accrual
Current year		137,852			122,740			104,314
Prior years		(301	)		(13,683	)		66,719
		137,551			109,057			171,033
Less: claims payments related to
Current year		20,180			17,517			15,243
Prior years		69,626			61,143			51,568
		89,806			78,660			66,811

Add: claims incurred in excess of retention limits		9,117			—			—

Balance at December 31,
Workers' compensation claims liabilities	$	312,537		$	255,675		$	225,278
Incurred but not reported (IBNR)	$	158,169		$	127,792		$	113,984

The Company is a self-insured employer with respect to workers' compensation coverage for all of its employees (including employees co-employed through our client service agreements) working in Colorado, Maryland and Oregon, except as described below. In the state of Washington, state law allows only the Company's staffing services and internal management employees to be covered under the Company's self-insured workers' compensation program.

Effective January 1, 2015, the Company stopped maintaining a certificate to self-insure in the state of California, and it now obtains individual policies from Chubb for all California-based clients along with clients in Delaware, Virginia, Pennsylvania, North Carolina, New Jersey, West Virginia and the District of Columbia. The arrangement with Chubb, known as a fronted program, provides BBSI a licensed, admitted insurance carrier to issue policies on behalf of BBSI. The risk of loss up to the first $5.0 million per claim is retained by BBSI through a reinsurance agreement. Chubb assumes credit risk should BBSI be unable to satisfy its indemnification obligations.

As part of its fronted workers’ compensation insurance program with Chubb, the Company makes monthly payments into a trust account (“the Chubb trust account”) to be used for the payment of future claims. The balance in the Chubb trust account was $277.1 million and $166.6 million at December 31, 2016 and December 31, 2015, respectively. The Chubb trust account balances are included as a component of the current and long-term restricted cash and investments in the consolidated balance sheets.

The surplus of Ecole was $12.1 million and $9.5 million at December 31, 2016 and 2015, respectively, and is included in long-term restricted cash and investments in the consolidated balance sheets.

The states of California, Maryland, Oregon, Washington, Colorado and Delaware required us to maintain specified investment balances or other financial instruments totaling $135.0 million and $156.8 million at December 31, 2016 and 2015, respectively, to cover potential workers’ compensation claims losses related to the Company’s current and former status as a self-insured employer. In addition to restricted cash and investments held to satisfy these requirements, at December 31, 2016, we have provided surety bonds and standby letters of credit totaling $128.8 million, including a California requirement of $123.3 million.

The Company provided a total of $312.5 million and $255.7 million at December 31, 2016 and 2015, respectively, as an estimated future liability for unsettled workers' compensation claims liabilities. Of this amount, $9.1 million represents case reserves incurred in excess of the Company’s retention limits at December 31, 2016. The accrual for costs incurred in excess of retention limits is offset by a receivable from excess insurance carriers of $9.1 million at December 31, 2016 that is included in other assets on the consolidated balance sheets. There was no workers’ compensation reserve in excess of retention limits in 2015.