Employee Benefit Plans (Details) $ in Thousands		3 Months Ended		9 Months Ended
	Jan. 01, 2015 USD ($) plan_participant	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)
Components of net periodic cost (benefit):
Service cost		$ 3,839	$ 1,845	$ 7,241	$ 5,530
Interest cost		7,012	6,694	20,814	20,002
Expected return on plan assets		(6,237)	(7,084)	(18,793)	(21,258)
Amortization of unrecognized prior service costs (benefits)		(150)	(159)	(452)	(520)
Amortization of losses (gains) from earlier periods		2,644	3,268	7,414	9,497
Net periodic cost (benefit)		7,108	4,564	16,224	13,251
Defined Benefit Pension Plan
Components of net periodic cost (benefit):
Service cost		3,417	1,521	6,087	4,538
Interest cost		6,384	5,996	18,948	17,990
Expected return on plan assets		(6,237)	(7,084)	(18,793)	(21,258)
Amortization of unrecognized prior service costs (benefits)		0	3	0	10
Amortization of losses (gains) from earlier periods		2,726	3,086	7,695	9,298
Net periodic cost (benefit)		6,290	3,522	13,937	10,578
Expected Employer contribution for the year				0
Post-Retirement Medical Plan
Components of net periodic cost (benefit):
Service cost		349	254	935	781
Interest cost		184	167	534	420
Expected return on plan assets		0	0	0	0
Amortization of unrecognized prior service costs (benefits)		(275)	(395)	(827)	(1,230)
Amortization of losses (gains) from earlier periods		(67)	16	(237)	(298)
Net periodic cost (benefit)		191	42	405	(327)
Expected Employer contribution for the year				803
Payments to plan		212	576	603	1,100
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	219	211
Interest cost		444	531	1,332	1,592
Expected return on plan assets		0	0	0	0
Amortization of unrecognized prior service costs (benefits)		125	233	375	700
Amortization of losses (gains) from earlier periods		(15)	166	(44)	497
Net periodic cost (benefit)		627	1,000	1,882	3,000
Expected Employer contribution for the year				3,336
Payments to plan		$ 834	$ 830	$ 2,502	$ 3,995