Employee Benefits (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended			0 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011	Jul. 06, 2012 Subsequent event
Compensation and Retirement Disclosure [Abstract]
Defined benefit plans	$ 1,593	$ 790	$ 3,186	$ 1,580
Defined contribution plan (401k plan) - company match	723	1,595	1,429	3,274
Other	462	353	918	701
Total retirement plan expense	2,778	2,738	5,533	5,555
Components of net periodic pension expense:
Interest cost	6,058	6,388	12,116	12,776
Expected return on plan assets	(6,268)	(6,656)	(12,536)	(13,312)
Net amortization and deferral	1,803	1,058	3,606	2,116
Funded status of plan					165,393
Maximum time extension of which benefit plan deficits may be funded under the Preservation of Access to Care for Medicare Beneficiaries and Pension Relief Act of 2010	15 years
Estimated future employer contributions in current year	$ 9,000		$ 9,000
Prior period average interest rates were calculated under previous legislation	2 years
Subsequent event:
Period average interest rates are calculated under current legislation						25 years