Employee Benefit Plans (Details) $ in Thousands		3 Months Ended		6 Months Ended
	Jan. 01, 2015 USD ($) plan_participant	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)
Components of net periodic cost (benefit):
Service cost		$ 1,701	$ 1,843	$ 3,402	$ 3,686
Interest cost		6,901	6,654	13,802	13,308
Expected return on plan assets		(6,278)	(7,087)	(12,556)	(14,174)
Amortization of unrecognized prior service costs (benefits)		(151)	(181)	(302)	(362)
Amortization of losses (gains) from earlier periods		2,385	3,115	4,770	6,229
Net periodic cost (benefit)		4,558	4,344	9,116	8,687
Defined Benefit Pension Plan
Components of net periodic cost (benefit):
Service cost		1,335	1,509	2,670	3,017
Interest cost		6,282	5,997	12,564	11,994
Expected return on plan assets		(6,278)	(7,087)	(12,556)	(14,174)
Amortization of unrecognized prior service costs (benefits)		0	3	0	7
Amortization of losses (gains) from earlier periods		2,485	3,106	4,970	6,212
Net periodic cost (benefit)		3,824	3,528	7,648	7,056
Expected Employer contribution for the year				0
Post-Retirement Medical Plan
Components of net periodic cost (benefit):
Service cost		293	264	586	528
Interest cost		175	126	350	253
Expected return on plan assets		0	0	0	0
Amortization of unrecognized prior service costs (benefits)		(276)	(417)	(552)	(835)
Amortization of losses (gains) from earlier periods		(85)	(157)	(170)	(315)
Net periodic cost (benefit)		107	(184)	214	(369)
Expected Employer contribution for the year				781
Payments to plan		187	391	391	524
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	146	141
Interest cost		444	531	888	1,061
Expected return on plan assets		0	0	0	0
Amortization of unrecognized prior service costs (benefits)		125	233	250	466
Amortization of losses (gains) from earlier periods		(15)	166	(30)	332
Net periodic cost (benefit)		627	1,000	1,254	2,000
Expected Employer contribution for the year				3,336
Payments to plan		$ 834	$ 830	$ 1,668	$ 3,165