Pension Plans and Other Postretirement Benefits (Details 3) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Fair value hierarchy for the Company's defined benefit pension plan assets
Total	$ 31,099		$ 35,722
United States [Member]
Fair value hierarchy for the Company's defined benefit pension plan assets
Total	12,718	[1]	14,730	[1]
International [Member]
Fair value hierarchy for the Company's defined benefit pension plan assets
Total	2,790	[1]	3,579	[1]
Fixed Income Funds [Member]
Fair value hierarchy for the Company's defined benefit pension plan assets
Total	15,591		17,413
Level 1 [Member]
Fair value hierarchy for the Company's defined benefit pension plan assets
Total	0		0
Level 1 [Member] | United States [Member]
Fair value hierarchy for the Company's defined benefit pension plan assets
Total	0	[1]	0	[1]
Level 1 [Member] | International [Member]
Fair value hierarchy for the Company's defined benefit pension plan assets
Total	0	[1]	0	[1]
Level 1 [Member] | Fixed Income Funds [Member]
Fair value hierarchy for the Company's defined benefit pension plan assets
Total	0		0
Level 2 [Member]
Fair value hierarchy for the Company's defined benefit pension plan assets
Total	31,099		35,722
Level 2 [Member] | United States [Member]
Fair value hierarchy for the Company's defined benefit pension plan assets
Total	12,718	[1]	14,730	[1]
Level 2 [Member] | International [Member]
Fair value hierarchy for the Company's defined benefit pension plan assets
Total	2,790	[1]	3,579	[1]
Level 2 [Member] | Fixed Income Funds [Member]
Fair value hierarchy for the Company's defined benefit pension plan assets
Total	15,591		17,413
Level 3 [Member]
Fair value hierarchy for the Company's defined benefit pension plan assets
Total	0		0
Level 3 [Member] | United States [Member]
Fair value hierarchy for the Company's defined benefit pension plan assets
Total	0	[1]	0	[1]
Level 3 [Member] | International [Member]
Fair value hierarchy for the Company's defined benefit pension plan assets
Total	0	[1]	0	[1]
Level 3 [Member] | Fixed Income Funds [Member]
Fair value hierarchy for the Company's defined benefit pension plan assets
Total	$ 0		$ 0

[1] None of the trust fund assets for the defined benefit pension plan have been invested in shares of HMEC’s common stock.