Employee Benefit Plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Change in plan assets
Fair value of plan assets at beginning of year	$ 116,022
Fair value of plan assets at end of year	285	$ 116,022
Pension Benefits
Change in benefit obligation
Benefit obligation at beginning of year	133,984	103,612
Service cost	236	180	$ 0
Interest cost	182	4,774	4,227
Actuarial (gains) losses	(6,299)	29,059
Participant contributions	0	0
Retiree drug subsidy received	0	0
Benefits paid	(119,426)	(3,641)
Benefit obligation at end of year	8,677	133,984	103,612
Change in plan assets
Fair value of plan assets at beginning of year	116,041	110,862
Actual gains on plan assets	517	8,689
Company contributions	3,153	131
Participant contributions	0	0
Benefits paid	(119,426)	(3,641)
Fair value of plan assets at end of year	285	116,041	110,862
Under funded status of plans at end of year	(8,392)	(17,943)
Postretirement Benefits
Change in benefit obligation
Benefit obligation at beginning of year	42,300	33,383
Service cost	900	687	841
Interest cost	1,584	1,511	1,366
Actuarial (gains) losses	(4,762)	7,341
Participant contributions	535	532
Retiree drug subsidy received	138	107
Benefits paid	(1,543)	(1,261)
Benefit obligation at end of year	39,152	42,300	33,383
Change in plan assets
Fair value of plan assets at beginning of year	0	0
Actual gains on plan assets	0	0
Company contributions	1,008	729
Participant contributions	535	532
Benefits paid	(1,543)	(1,261)
Fair value of plan assets at end of year	0	0	$ 0
Under funded status of plans at end of year	$ (39,152)	$ (42,300)