Basis of Presentation and Consolidation (Schedule of Reclassifciations Out of Accumulated Other Comprehensive Income) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012	Sep. 30, 2013		Sep. 30, 2012
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	$ 28,387		$ 24,324	$ 97,990		$ 98,120
Income tax provision	(10,348)		(9,133)	(36,907)		(36,730)
Net income	18,039		15,191	61,083		61,390
Defined Benefit Plan Items | Amount Reclassified from Accumulated Other Comprehensive Income
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Amortization of prior-service cost	(136)	[1],[2]		(408)	[1],[2]
Income before income taxes	(136)	[2]		(408)	[2]
Income tax provision	51	[2]		153	[2]
Net income	$ (85)	[2]		$ (255)	[2]

[1] This accumulated other comprehensive income component is included in the computation of net periodic pension cost (see Note 6. Employee Benefit Plans footnote for additional details).

[2] Amounts in parentheses indicate debits to profit/loss