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		$ 402,269	$ 393,393
Fair value of plan assets at Dec. 31		378,913	402,269	$ 393,393
Level 3
Changes in Level 3 Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1		25,020	23,977	30,104
Net realized gains (losses)		5,319	3,532	2,308
Net unrealized gains (losses)		(1,988)	(2,113)	420
Purchases, issuances and settlements, net		(1,525)	(376)	726
Transfers in (out) of Level 3		0	0	(9,581)	[1]
Fair value of plan assets at Dec. 31		26,826	25,020	23,977
Asset-backed securities
Changes in Level 3 Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1		494
Fair value of plan assets at Dec. 31		323	494
Asset-backed securities | Level 3
Changes in Level 3 Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1		0	0	1,755
Net realized gains (losses)				0
Net unrealized gains (losses)				0
Purchases, issuances and settlements, net				0
Transfers in (out) of Level 3	[1]			(1,755)
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		1,451
Fair value of plan assets at Dec. 31			1,451
Mortgage-backed securities | Level 3
Changes in Level 3 Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1		0	0	4,331
Net realized gains (losses)				0
Net unrealized gains (losses)				0
Purchases, issuances and settlements, net				0
Transfers in (out) of Level 3	[1]			(4,331)
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		18,331	18,222
Fair value of plan assets at Dec. 31		19,114	18,331	18,222
Private equity investments | Level 3
Changes in Level 3 Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1		18,331	18,222	17,049
Net realized gains (losses)		4,248	3,101	2,630
Net unrealized gains (losses)		(1,541)	(1,894)	(1,055)
Purchases, issuances and settlements, net		(1,924)	(1,098)	(402)
Transfers in (out) of Level 3		0	0	0	[1]
Fair value of plan assets at Dec. 31		19,114	18,331	18,222
Real estate
Changes in Level 3 Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1		6,689	5,755
Fair value of plan assets at Dec. 31		7,712	6,689	5,755
Real estate | Level 3
Changes in Level 3 Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1		6,689	5,755	6,969
Net realized gains (losses)		1,071	431	(322)
Net unrealized gains (losses)		(447)	(219)	1,475
Purchases, issuances and settlements, net		399	722	1,128
Transfers in (out) of Level 3		0	0	(3,495)	[1]
Fair value of plan assets at Dec. 31		$ 7,712	$ 6,689	$ 5,755

[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.