Shareholders' Equity (Narrative) (Details) (USD $)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Shareholders Equity and Share-Based Payments [Line Items]
Compensation cost	$ 916,000	$ 1,119,000
Total income tax benefit recognized related to stock-based compensation	366,000	448,000
Total intrinsic value of options exercised	7,000	115,000
Cash received from exercise of stock options	20,000	212,000
Restricted stock units at fair value	0	677,000
Restricted stock share based compensation arrangement by share based payment award, award vesting period prior to 2011	5
Restricted stock share based compensation arrangement by share based payment award, award vesting period after 2011	3
Income tax benefits received	622,000	457,000
Tax deficiency from stock options exercised	42,000	233,000
Nonvested Stock [Member]
Shareholders Equity and Share-Based Payments [Line Items]
Total unrecognized compensation cost related to nonvested stock options	2,400,000
Expected recognized over a weighted-average period, years	2.2
Restricted Stock [Member]
Shareholders Equity and Share-Based Payments [Line Items]
Total fair value of restricted stock units vested and released	1,600,000	651,000
Total unrecognized compensation cost related to nonvested stock options	6,700,000
Expected recognized over a weighted-average period, years	2.7
Restricted Shares [Member]
Shareholders Equity and Share-Based Payments [Line Items]
Total unrecognized compensation cost related to nonvested stock options	$ 890,000
Expected recognized over a weighted-average period, years	2.0