Benefit Plans Benefit Plans - Textuals (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Period of Return for Fixed Income Investments From Discount Rate Assumptions	20 years
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlements, plan assets	$ 62,754	$ 0
Employer contributions	15,711	23,318
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	3,343
Settlement loss	21,907	0	0
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlements, plan assets	0	0
Employer contributions	1,861	2,247
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	1,798
Settlement loss	$ 0	$ 0	$ 0
Prior to July 1, 2003 Hire Date [Member] | Effective April 1, 2009 to December 31, 2010 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Employer Matching Contribution, Percent	0.00%
Employee Contributions First Six Percent [Member] | Prior to July 1, 2003 Hire Date [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Participant Contribution Percentage	6.00%
Employee Contributions First Six Percent [Member] | Prior to July 1, 2003 Hire Date [Member] | Effective January 1, 2011 to December 31, 2011 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Employer Matching Contribution, Percent	25.00%
Employee Contributions First Six Percent [Member] | Prior to July 1, 2003 Hire Date [Member] | Effective January 1, 2012 to December 31, 2012 [Domain]
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Employer Matching Contribution, Percent	30.00%
Employee Contributions First Six Percent [Member] | Subsequent to July 1, 2003 Hire Date [Member] | Effective April 1, 2009 to December 31, 2010 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Employer Matching Contribution, Percent	30.00%
Employee Contributions First Six Percent [Member] | Subsequent to July 1, 2003 Hire Date [Member] | Effective January 1, 2011 to December 31, 2011 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Employer Matching Contribution, Percent	55.00%
Employee Contributions First Six Percent [Member] | Subsequent to July 1, 2003 Hire Date [Member] | Effective January 1, 2012 to December 31, 2012 [Domain]
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Employer Matching Contribution, Percent	60.00%