Employee Benefit Plans (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Amounts recognized in consolidated balance sheets:
Accumulated other comprehensive income (loss)	$ (194,181)	$ (207,732)
Information regarding amounts in accumulated other comprehensive income (loss) that have not yet been recognized as components of net periodic benefit cost
Net gain (loss), gross	(131,190)
Net prior service (cost) credit, Gross	(476)
Amounts in accumulated other comprehensive income (loss) that have not yet been recognized as components of net periodic benefit cost, Gross	(131,666)
Net gain (loss), Net of tax	(85,273)
Net prior service (cost) credit, Net of tax	(310)
Amounts in accumulated other comprehensive income (loss) that have not yet been recognized as components of net periodic benefit cost, Net of tax	(85,583)
Amounts in accumulated other comprehensive income (loss) that are expected to be recognized as components of net periodic benefit costs during the next fiscal year
Net gain (loss), Gross	(9,538)
Net prior service (cost) credit, Gross	601
Amounts in accumulated other comprehensive income (loss) that are expected to be recognized as components of net periodic benefit costs during the next fiscal year, Gross	(8,937)
Net gain (loss), Net of tax	(6,199)
Net prior service (cost) credit, Net of tax	390
Amounts in accumulated other comprehensive income (loss) that are expected to be recognized as components of net periodic benefit costs during the next fiscal year, Net of tax	(5,809)
Other liabilities
Amounts recognized in consolidated balance sheets:
Accumulated other comprehensive income (loss)	(194,181)	(207,732)
Accumulated other comprehensive income (loss)
Amounts recognized in consolidated balance sheets:
Accumulated other comprehensive income (loss)	(131,666)	(163,252)
Defined Benefit Pension Plan
Amounts recognized in consolidated balance sheets:
Accumulated other comprehensive income (loss)	(133,686)	(139,118)
Information regarding amounts in accumulated other comprehensive income (loss) that have not yet been recognized as components of net periodic benefit cost
Net gain (loss), gross	(139,316)
Net prior service (cost) credit, Gross	0
Amounts in accumulated other comprehensive income (loss) that have not yet been recognized as components of net periodic benefit cost, Gross	(139,316)
Net gain (loss), Net of tax	(90,555)
Net prior service (cost) credit, Net of tax	0
Amounts in accumulated other comprehensive income (loss) that have not yet been recognized as components of net periodic benefit cost, Net of tax	(90,555)
Amounts in accumulated other comprehensive income (loss) that are expected to be recognized as components of net periodic benefit costs during the next fiscal year
Net gain (loss), Gross	(9,940)
Net prior service (cost) credit, Gross	0
Amounts in accumulated other comprehensive income (loss) that are expected to be recognized as components of net periodic benefit costs during the next fiscal year, Gross	(9,940)
Net gain (loss), Net of tax	(6,461)
Net prior service (cost) credit, Net of tax	0
Amounts in accumulated other comprehensive income (loss) that are expected to be recognized as components of net periodic benefit costs during the next fiscal year, Net of tax	(6,461)
Defined Benefit Pension Plan | Other liabilities
Amounts recognized in consolidated balance sheets:
Accumulated other comprehensive income (loss)	(133,686)	(139,118)
Defined Benefit Pension Plan | Accumulated other comprehensive income (loss)
Amounts recognized in consolidated balance sheets:
Accumulated other comprehensive income (loss)	(139,316)	(165,652)
Post-Retirement Medical Plan
Amounts recognized in consolidated balance sheets:
Accumulated other comprehensive income (loss)	(16,637)	(12,782)
Information regarding amounts in accumulated other comprehensive income (loss) that have not yet been recognized as components of net periodic benefit cost
Net gain (loss), gross	6,815
Net prior service (cost) credit, Gross	1,725
Amounts in accumulated other comprehensive income (loss) that have not yet been recognized as components of net periodic benefit cost, Gross	8,540
Net gain (loss), Net of tax	4,430
Net prior service (cost) credit, Net of tax	1,121
Amounts in accumulated other comprehensive income (loss) that have not yet been recognized as components of net periodic benefit cost, Net of tax	5,551
Amounts in accumulated other comprehensive income (loss) that are expected to be recognized as components of net periodic benefit costs during the next fiscal year
Net gain (loss), Gross	341
Net prior service (cost) credit, Gross	1,102
Amounts in accumulated other comprehensive income (loss) that are expected to be recognized as components of net periodic benefit costs during the next fiscal year, Gross	1,443
Net gain (loss), Net of tax	222
Net prior service (cost) credit, Net of tax	716
Amounts in accumulated other comprehensive income (loss) that are expected to be recognized as components of net periodic benefit costs during the next fiscal year, Net of tax	938
Post-Retirement Medical Plan | Other liabilities
Amounts recognized in consolidated balance sheets:
Accumulated other comprehensive income (loss)	(16,637)	(12,782)
Post-Retirement Medical Plan | Accumulated other comprehensive income (loss)
Amounts recognized in consolidated balance sheets:
Accumulated other comprehensive income (loss)	8,540	14,390
Supplemental Executive Retirement Plan
Amounts recognized in consolidated balance sheets:
Accumulated other comprehensive income (loss)	(43,858)	(55,832)
Information regarding amounts in accumulated other comprehensive income (loss) that have not yet been recognized as components of net periodic benefit cost
Net gain (loss), gross	1,311
Net prior service (cost) credit, Gross	(2,201)
Amounts in accumulated other comprehensive income (loss) that have not yet been recognized as components of net periodic benefit cost, Gross	(890)
Net gain (loss), Net of tax	852
Net prior service (cost) credit, Net of tax	(1,431)
Amounts in accumulated other comprehensive income (loss) that have not yet been recognized as components of net periodic benefit cost, Net of tax	(579)
Amounts in accumulated other comprehensive income (loss) that are expected to be recognized as components of net periodic benefit costs during the next fiscal year
Net gain (loss), Gross	61
Net prior service (cost) credit, Gross	(501)
Amounts in accumulated other comprehensive income (loss) that are expected to be recognized as components of net periodic benefit costs during the next fiscal year, Gross	(440)
Net gain (loss), Net of tax	40
Net prior service (cost) credit, Net of tax	(326)
Amounts in accumulated other comprehensive income (loss) that are expected to be recognized as components of net periodic benefit costs during the next fiscal year, Net of tax	(286)
Supplemental Executive Retirement Plan | Other liabilities
Amounts recognized in consolidated balance sheets:
Accumulated other comprehensive income (loss)	(43,858)	(55,832)
Supplemental Executive Retirement Plan | Accumulated other comprehensive income (loss)
Amounts recognized in consolidated balance sheets:
Accumulated other comprehensive income (loss)	$ (890)	$ (11,990)