Benefit Plans and Other Postretirement Benefits, Changes in Level 3 Postretirement Benefit Plan Assets (Details) (Postretirement Benefit Plan, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2014
Changes in Level 3 Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1				$ 512
Fair value of plan assets at Dec. 31	746		647	512
Level 3
Changes in Level 3 Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1	55		62	0
Net realized gains (losses)	0		(1)
Net unrealized gains (losses)	0		9
Purchases, issuances and settlements, net	0		(15)
Transfers in (out) of Level 3	(55)	[1]	0
Fair value of plan assets at Dec. 31	0		55	0
Asset-backed securities
Changes in Level 3 Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1				4
Fair value of plan assets at Dec. 31	5			4
Asset-backed securities | Level 3
Changes in Level 3 Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1	1		14	0
Net realized gains (losses)	0		0
Net unrealized gains (losses)	0		3
Purchases, issuances and settlements, net	0		(16)
Transfers in (out) of Level 3	(1)	[1]	0
Fair value of plan assets at Dec. 31	0		1	0
Mortgage-backed securities
Changes in Level 3 Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1				12
Fair value of plan assets at Dec. 31	37			12
Mortgage-backed securities | Level 3
Changes in Level 3 Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1	54		48	0
Net realized gains (losses)	0		(1)
Net unrealized gains (losses)	0		6
Purchases, issuances and settlements, net	0		1
Transfers in (out) of Level 3	(54)	[1]	0
Fair value of plan assets at Dec. 31	$ 0		$ 54	$ 0

[1] Transfers out of Level 3 into Level 2 were principally due to diminished use of unobservable inputs that were previously significant to these fair value measurements and were subsequently sold during 2013.