Leases (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating Leased Assets [Line Items]
Rent expense under operating lease	$ 14,376	$ 13,325	$ 13,185
Longest lease expiration date	Sep. 30, 2023	Dec. 31, 2015
Gross rents [Abstract]
2013	14,207
2014	12,282
2015	5,965
2016	4,138
2017	3,487
Thereafter	3,023
Gross rents, Total	43,102
Operating Leases Subleases [Abstract]
2013	(1,107)
2014	(1,093)
2015	(415)
2016	(362)
2017	(362)
Thereafter	(175)
Operating Leases Subleases, Total	(3,514)
Net rents [Abstract]
2013	13,100
2014	11,189
2015	5,550
2016	3,776
2017	3,125
Thereafter	2,848
Net rents, Total	39,588
Land and buildings [Member]
Operating Leased Assets [Line Items]
Rent expense under operating lease	$ 585	$ 583	$ 574