Employee Benefit Plans (Details) $ in Thousands		3 Months Ended
	Jan. 01, 2015 USD ($) plan_participant	Mar. 31, 2016 USD ($)	Mar. 31, 2015 USD ($)
Components of net periodic cost (benefit):
Service cost		$ 1,701	$ 1,843
Interest cost		6,901	6,654
Expected return on plan assets		(6,278)	(7,087)
Amortization of unrecognized prior service costs (benefits)		(151)	(181)
Amortization of losses (gains) from earlier periods		2,385	3,115
Net periodic cost (benefit)		4,558	4,344
Defined Benefit Pension Plan
Components of net periodic cost (benefit):
Service cost		1,335	1,509
Interest cost		6,282	5,997
Expected return on plan assets		(6,278)	(7,087)
Amortization of unrecognized prior service costs (benefits)		0	3
Amortization of losses (gains) from earlier periods		2,485	3,106
Net periodic cost (benefit)		3,824	3,528
Expected Employer contribution for the year		0
Post-Retirement Medical Plan
Components of net periodic cost (benefit):
Service cost		293	264
Interest cost		175	126
Expected return on plan assets		0	0
Amortization of unrecognized prior service costs (benefits)		(276)	(417)
Amortization of losses (gains) from earlier periods		(85)	(157)
Net periodic cost (benefit)		107	(184)
Expected Employer contribution for the year		816
Payments to plan		204	133
Post-Retirement Medical Plan | Putnam
Components of net periodic cost (benefit):
Number of individuals | plan_participant	150
Post-Retirement Medical Plan | Other Liabilities | Putnam
Components of net periodic cost (benefit):
Prior service cost	$ 339
Supplemental Executive Retirement Plan
Components of net periodic cost (benefit):
Service cost		73	70
Interest cost		444	531
Expected return on plan assets		0	0
Amortization of unrecognized prior service costs (benefits)		125	233
Amortization of losses (gains) from earlier periods		(15)	166
Net periodic cost (benefit)		627	1,000
Expected Employer contribution for the year		3,337
Payments to plan		$ 834	$ 2,335