Dividends (Dividends Paid) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2013	Mar. 31, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Dividends [Abstract]
Cash dividend per common share	$ 0.16750	$ 0.16625
Cash dividend per common share based on weighted average number of shares	$ 0.17		$ 0.16	$ 0.33	$ 0.32
Total cash dividends paid	$ 11,516	$ 11,415		$ 22,931	$ 21,803
Record date	May 10, 2013	Feb. 22, 2013
Payment date	Jun. 14, 2013	Mar. 15, 2013