Benefit Plans and Other Postretirement Benefits, Changes in Level 3 Postretirement Benefit Plan Assets (Details) (Postretirement Benefit Plan [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Changes in Level 3 Plan Assets [Roll Forward]
Fair value of plan assets at Dec. 31	$ 647	$ 746	$ 992
Level 3 [Member]
Changes in Level 3 Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1	62	51	198
Net realized gains (losses)	(1)	(3)	(3)
Net unrealized gains (losses)	9	4	20
Purchases, issuances and settlements, net	(15)	10	(164)
Fair value of plan assets at Dec. 31	55	62	51
Asset-backed Securities [Member]
Changes in Level 3 Plan Assets [Roll Forward]
Fair value of plan assets at Dec. 31	1	14
Asset-backed Securities [Member] | Level 3 [Member]
Changes in Level 3 Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1	14	6	30
Net realized gains (losses)	0	0	(1)
Net unrealized gains (losses)	3	(2)	4
Purchases, issuances and settlements, net	(16)	10	(27)
Fair value of plan assets at Dec. 31	1	14	6
Mortgage-backed Securities [Member]
Changes in Level 3 Plan Assets [Roll Forward]
Fair value of plan assets at Dec. 31	54	48
Mortgage-backed Securities [Member] | Level 3 [Member]
Changes in Level 3 Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1	48	45	168
Net realized gains (losses)	(1)	(3)	(2)
Net unrealized gains (losses)	6	6	16
Purchases, issuances and settlements, net	1	0	(137)
Fair value of plan assets at Dec. 31	$ 54	$ 48	$ 45