Fair value measurements Changes in Level 3 Assets (Details) - Level 3 - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Pension benefits
Changes in Level 3 assets
Balance at the beginning of the period	$ 580	$ 581
Realized and unrealized losses	(203)	(1)
Purchases and settlements, net	(282)	0
Balance at the end of the period	95	580
Other benefits
Changes in Level 3 assets
Balance at the beginning of the period	18	18
Realized and unrealized losses	(6)	0
Purchases and settlements, net	(8)	0
Balance at the end of the period	$ 4	$ 18