Pension Plans and Other Postretirement Benefits (Details 2) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013
Defined Benefit Plan [Member]
Summary of minimum funding requirement, contributions made and the expected full year contributions for the Company's plans
Minimum funding requirement for 2013	$ 0
Contributions made in the nine months ended September 30, 2013	3,103
Expected contributions (approximations) for the year ended December 31, 2013 as of the time of:
This Form 10-Q (1)	3,103	[1]
2012 Form 10-K (2)	2,500	[2]
Supplemental Defined Benefit Plans [Member]
Summary of minimum funding requirement, contributions made and the expected full year contributions for the Company's plans
Contributions made in the nine months ended September 30, 2013	986
Expected contributions (approximations) for the year ended December 31, 2013 as of the time of:
This Form 10-Q (1)	1,320	[1]
2012 Form 10-K (2)	1,320	[2]
Other Postretirement Benefits [Member]
Summary of minimum funding requirement, contributions made and the expected full year contributions for the Company's plans
Contributions made in the nine months ended September 30, 2013	406
Expected contributions (approximations) for the year ended December 31, 2013 as of the time of:
This Form 10-Q (1)	480	[1]
2012 Form 10-K (2)	$ 480	[2]

[1] HMEC’s Quarterly Report on Form 10-Q for the quarter ended September 30, 2013.

[2] HMEC’s Annual Report on Form 10-K for the year ended December 31, 2012, specifically “Notes to Consolidated Financial Statements — Note 9 — Pension Plans and Other Postretirement Benefits”.