Share-Based Compensation Arrangements (Narrative) (Details) (USD $)	12 Months Ended																				12 Months Ended
	Dec. 31, 2012 plan	Dec. 31, 2012 Share Options [Member]	Dec. 31, 2011 Share Options [Member]	Dec. 31, 2010 Share Options [Member]	Dec. 31, 2012 Time Based Nonvested Shares [Member]	Dec. 31, 2011 Time Based Nonvested Shares [Member]	Dec. 31, 2010 Time Based Nonvested Shares [Member]	Dec. 31, 2012 Performance Based Nonvested Shares [Member]	Dec. 31, 2011 Performance Based Nonvested Shares [Member]	Dec. 31, 2010 Performance Based Nonvested Shares [Member]	Dec. 31, 2012 Minimum [Member] Time Based Nonvested Shares [Member]	Dec. 31, 2011 Minimum [Member] Time Based Nonvested Shares [Member]	Dec. 31, 2010 Minimum [Member] Time Based Nonvested Shares [Member]	Dec. 31, 2012 Maximum [Member] Time Based Nonvested Shares [Member]	Dec. 31, 2011 Maximum [Member] Time Based Nonvested Shares [Member]	Dec. 31, 2010 Maximum [Member] Time Based Nonvested Shares [Member]	Apr. 22, 2003 2003 Stock Incentive Plan [Member]	Apr. 22, 2003 2003 Stock Incentive Plan [Member] Stock Options and Stock Appreciation Rights [Member]	Apr. 28, 2009 Amended and Restated 2003 Stock Incentive Plan [Member]	Apr. 28, 2009 Amended and Restated 2003 Stock Incentive Plan [Member] Stock Options and Stock Appreciation Rights [Member]	Dec. 31, 2012 Amended and Restated 2003 Stock Incentive Plan [Member] Share Options [Member]	Dec. 31, 2012 Amended and Restated 2003 Stock Incentive Plan [Member] Performance Based Nonvested Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of plans	2
Shares authorized																	600,000	200,000	1,200,000	400,000
Expiration period																					10 years
Equity instruments other than options minimum shares earned to target percentage																						0.00%
Equity instruments other than options maximum shares earned to target percentage																						200.00%
Options granted		106,775	57,450	83,700
Award vesting period		3 years	3 years	3 years				3 years	3 years	3 years	3 years	3 years	3 years	5 years	5 years	5 years
Share options granted weighted average grant date fair value		$ 7.46	$ 7.46	$ 6.29
Share options exercised total intrinsic value		$ 812,000	$ 493,000	$ 349,000
Equity instruments other than options granted					29,725	31,950	56,500	47,208
Equity instruments other than options granted, grant date fair value								$ 23.65	$ 21.62	$ 15.11
Equity instruments other than options, minimum shares earned								0	0	0
Equity instruments other than options, maximum shares earned								61,600	73,502	25,000
Equity instruments other than options, shares vesting percentages								160.00%	155.00%	148.00%
Equity instruments other than options, shares vesting								49,340	51,180	18,500
Total unrecognized compensation cost	$ 3,200,000
Weighted average recognition period (in years)	2 years