Defined Benefit Pension Plans Defined Benefit Pension Plan Additional Information (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Contributions by Employer	$ 42,000	$ 321,000	$ 440,000
Estimated Future Employer Contributions in Current Fiscal Year	$ 564,000