Employee Benefit Plans (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Amounts recognized in consolidated balance sheets:
Accumulated other comprehensive income (loss)	$ (188,917)	$ (120,266)
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	(190,294)
Net prior service (cost) credit, Gross	1,377
Amounts in accumulated other comprehensive income (loss) that have not yet been recognized as components of net periodic benefit cost, Gross	(188,917)
Net gain (loss), Net of tax	(123,690)
Net prior service (cost) credit, Net of tax	895
Amounts in accumulated other comprehensive income (loss) that have not yet been recognized as components of net periodic benefit cost, Net of tax	(122,795)
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	(16,464)
Net prior service (cost) credit, Gross	666
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	(15,798)
Net gain (loss), Net of tax	(10,702)
Net prior service (cost) credit, Net of tax	433
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	(10,269)
Other assets
Amounts recognized in consolidated balance sheets:
Accumulated other comprehensive income (loss)		12,690
Other liabilities
Amounts recognized in consolidated balance sheets:
Accumulated other comprehensive income (loss)	(246,760)	(193,571)
Accumulated other comprehensive income (loss)
Amounts recognized in consolidated balance sheets:
Accumulated other comprehensive income (loss)	(188,917)	(120,266)
Defined benefit pension plan
Amounts recognized in consolidated balance sheets:
Accumulated other comprehensive income (loss)	(180,869)	(120,487)
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	(180,754)
Net prior service (cost) credit, Gross	(115)
Amounts in accumulated other comprehensive income (loss) that have not yet been recognized as components of net periodic benefit cost, Gross	(180,869)
Net gain (loss), Net of tax	(117,490)
Net prior service (cost) credit, Net of tax	(75)
Amounts in accumulated other comprehensive income (loss) that have not yet been recognized as components of net periodic benefit cost, Net of tax	(117,565)
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	(15,577)
Net prior service (cost) credit, Gross	(51)
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	(15,628)
Net gain (loss), Net of tax	(10,125)
Net prior service (cost) credit, Net of tax	(33)
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	(10,158)
Defined benefit pension plan | Other assets
Amounts recognized in consolidated balance sheets:
Accumulated other comprehensive income (loss)		12,690
Defined benefit pension plan | Other liabilities
Amounts recognized in consolidated balance sheets:
Accumulated other comprehensive income (loss)	(164,069)	(120,488)
Defined benefit pension plan | Accumulated other comprehensive income (loss)
Amounts recognized in consolidated balance sheets:
Accumulated other comprehensive income (loss)	(180,869)	(120,487)
Post-retirement medical plan
Amounts recognized in consolidated balance sheets:
Accumulated other comprehensive income (loss)	12,662	15,741
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	6,170
Net prior service (cost) credit, Gross	6,492
Amounts in accumulated other comprehensive income (loss) that have not yet been recognized as components of net periodic benefit cost, Gross	12,662
Net gain (loss), Net of tax	4,011
Net prior service (cost) credit, Net of tax	4,220
Amounts in accumulated other comprehensive income (loss) that have not yet been recognized as components of net periodic benefit cost, Net of tax	8,231
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	413
Net prior service (cost) credit, Gross	1,650
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	2,063
Net gain (loss), Net of tax	268
Net prior service (cost) credit, Net of tax	1,072
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	1,340
Post-retirement medical plan | Other liabilities
Amounts recognized in consolidated balance sheets:
Accumulated other comprehensive income (loss)	(13,462)	(11,725)
Post-retirement medical plan | Accumulated other comprehensive income (loss)
Amounts recognized in consolidated balance sheets:
Accumulated other comprehensive income (loss)	12,662	15,741
Supplemental executive retirement plan
Amounts recognized in consolidated balance sheets:
Accumulated other comprehensive income (loss)	(20,710)	(15,520)
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	(15,710)
Net prior service (cost) credit, Gross	(5,000)
Amounts in accumulated other comprehensive income (loss) that have not yet been recognized as components of net periodic benefit cost, Gross	(20,710)
Net gain (loss), Net of tax	(10,211)
Net prior service (cost) credit, Net of tax	(3,250)
Amounts in accumulated other comprehensive income (loss) that have not yet been recognized as components of net periodic benefit cost, Net of tax	(13,461)
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	(1,300)
Net prior service (cost) credit, Gross	(933)
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	(2,233)
Net gain (loss), Net of tax	(845)
Net prior service (cost) credit, Net of tax	(606)
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	(1,451)
Supplemental executive retirement plan | Other liabilities
Amounts recognized in consolidated balance sheets:
Accumulated other comprehensive income (loss)	(69,229)	(61,358)
Supplemental executive retirement plan | Accumulated other comprehensive income (loss)
Amounts recognized in consolidated balance sheets:
Accumulated other comprehensive income (loss)	$ (20,710)	$ (15,520)