Employee Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2012

Employee Benefit Plans

Schedule of employee benefit plan expenses

Our consolidated statements of operations include expenses in connection with employee benefit plans, as follows for the years ended December 31 (in thousands):

	2012		2011		2010
Cloud Peak Energy defined contribution retirement plans	$	12,550	$	12,496	$	11,212
Cloud Peak Energy retiree medical plan		7,212		5,602		4,710
		19,762		18,098		15,922
Decker pension plan		889		672		626
Total	$	20,651	$	18,770	$	16,548

Schedule of total contributions during the period to defined contribution retirement plans

Total contributions for the years ended December 31 are as follows (in thousands):

	2012		2011		2010
Contributions	$	12,550	$	12,496	$	11,212

Schedule of components of net periodic postretirement benefit cost

Net periodic postretirement benefit costs included the following components (in thousands):

	2012		2011		2010
Service cost	$	4,213	$	3,016	$	2,316
Interest cost		1,424		1,281		989
Amortization of prior service cost		1,575		1,305		1,406
Net periodic postretirement benefit cost	$	7,212	$	5,602	$	4,711

Schedule of assumptions in the measurement of the APBO

	2012			2011			2010
Discount rate		3.87	%		4.30	%		5.51	%
Health care cost trend rate assumed for next year		7.50	%		8.00	%		8.50	%
Ultimate health care cost trend rate		5.00	%		5.00	%		5.00	%
Year that the rate reaches the ultimate trend rate		2018			2018			2018

Schedule of changes in accumulated postretirement benefit obligation ("APBO")

Annually, we remeasure and adjust the liability for the accumulated postretirement benefit obligation ("APBO"). Changes in the APBO include the following components (in thousands):

	2012		2011		2010
Beginning Balance	$	33,166	$	23,271	$	16,379
Current period service costs		4,213		3,015		2,316
Interest costs		1,424		1,282		989
Change in actuarial assumptions		4,590		5,598		3,587
Ending Balance		43,393		33,166		23,271
Less current portion		231		37		37
Long-term APBO	$	43,162	$	33,129	$	23,234

Schedule of estimated future benefit payments under the Retiree Medical Plan, net of estimated employee contributions

Our estimated future benefit payments under the Retiree Medical Plan, which are net of estimated employee contributions and reflect expected future service, are as follows for the years ended December 31 (in thousands):

2013	$	231
2014		385
2015		578
2016		826
2017		1,149
2018 - 2022		11,519