Benefit Plans and Other Postretirement Benefits, Changes in Level 3 Pension Plan Assets (Details) - Pension Plans - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Changes in Level 3 Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1		$ 132,713	$ 136,935
Fair value of plan assets at Dec. 31		119,314	132,713	$ 136,935
Level 3
Changes in Level 3 Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1		9,588	9,801	14,894
Net realized gains (losses)		1,660	1,363	954
Net unrealized gains (losses)		(2,392)	(1,431)	(1,713)
Purchases, issuances and settlements, net		(476)	(145)	284
Transfers in (out) of Level 3		0	0	(4,618)	[1]
Fair value of plan assets at Dec. 31		8,380	9,588	9,801
Asset-backed securities
Changes in Level 3 Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1		162
Fair value of plan assets at Dec. 31		101	162
Asset-backed securities | Level 3
Changes in Level 3 Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1		0	0	749
Net realized gains (losses)				0
Net unrealized gains (losses)				0
Purchases, issuances and settlements, net				0
Transfers in (out) of Level 3	[1]			(749)
Fair value of plan assets at Dec. 31		0	0	0
Mortgage-backed securities
Changes in Level 3 Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1		475
Fair value of plan assets at Dec. 31			475
Mortgage-backed securities | Level 3
Changes in Level 3 Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1		0	0	2,128
Net realized gains (losses)				0
Net unrealized gains (losses)				0
Purchases, issuances and settlements, net				0
Transfers in (out) of Level 3	[1]			(2,128)
Fair value of plan assets at Dec. 31			0	0
Private equity investments
Changes in Level 3 Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1		7,078
Fair value of plan assets at Dec. 31		5,967	7,078
Private equity investments | Level 3
Changes in Level 3 Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1		7,078	7,502	8,545
Net realized gains (losses)		1,326	1,197	1,083
Net unrealized gains (losses)		(1,836)	(1,197)	(1,960)
Purchases, issuances and settlements, net		(601)	(424)	(166)
Transfers in (out) of Level 3		0	0	0	[1]
Fair value of plan assets at Dec. 31		5,967	7,078	7,502
Real estate
Changes in Level 3 Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1		2,510
Fair value of plan assets at Dec. 31		2,413	2,510
Real estate | Level 3
Changes in Level 3 Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1		2,510	2,299	3,472
Net realized gains (losses)		334	166	(129)
Net unrealized gains (losses)		(556)	(234)	247
Purchases, issuances and settlements, net		125	279	450
Transfers in (out) of Level 3		0	0	(1,741)	[1]
Fair value of plan assets at Dec. 31		$ 2,413	$ 2,510	$ 2,299

[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.