Pension, Postretirement and Postemployment Benefits (Details) (Pension Benefits, USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension Benefits
Change in benefit obligation:
Benefit obligation at beginning of year	$ 26,659,000	$ 20,628,000
Remeasurement		1,517,000
Interest cost	1,116,000	1,198,000	1,116,000
Actuarial loss (gain)	2,017,000	3,975,000
Benefit payments	(677,000)	(659,000)
Benefit obligation at end of year	29,205,000	26,659,000	20,628,000
Change in plan assets:
Fair value of plan assets at beginning of year	16,352,000	15,219,000
Actual (loss) return on plan assets	1,598,000	480,000
Employer contribution	1,507,000	1,312,000
Benefit payments	(677,000)	(659,000)
Fair value of plan assets at end of year	18,780,000	16,352,000	15,219,000
Funded status:
Underfunded status at end of year	(10,425,000)	(10,307,000)
Amounts recognized in consolidated balance sheets:
Other long-term liabilities	(10,425,000)	(10,307,000)
Components of net periodic benefit cost (recognized in our consolidated statements of income):
Interest cost	1,116,000	1,198,000	1,116,000
Expected return on plan assets	(1,086,000)	(1,008,000)	(909,000)
Recognized net actuarial loss	1,034,000	628,000	457,000
Net periodic benefit cost	1,064,000	818,000	664,000
Weighted-average assumptions:
Weighted-average discount rate (as a percent)	3.75%	4.25%	5.50%
Expected long-term rate of return on plan assets (as a percent)	6.50%	6.50%	6.50%
Net actuarial loss included in accumulated other comprehensive income (loss)	(12,700,000)	(12,100,000)	(6,700,000)
Amount expected to recognize as a components of net periodic benefit costs	$ 1,100,000