Stock Options And Employee Stock Purchase Plan (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Allocated Share-based Compensation Expense	$ 2,191,000	$ 2,425,000	$ 6,538,000	$ 7,108,000
Number of options outstanding	735,951		735,951		1,175,657
Number of options granted			0
Cash received upon the issuance of common stock			199,000	161,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Total Intrinsic Value			14,500,000	11,600,000
Stock Options [Member]
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	1,000,000		1,000,000		2,000,000
Restricted Stock And Restricted Stock Unit (RSU) [Member]
Allocated Share-based Compensation Expense	1,900,000	1,800,000	5,500,000	5,000,000
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	22,600,000		22,600,000		20,200,000
Restricted Stock [Member]
Shares, Granted			176,864
Weighted-Average Grant-Date Fair Value, Granted			$ 44.65
Number of stocks outstanding	858,155		858,155		1,178,371
Restricted Stock Units (RSUs) [Member]
Shares, Granted			16,737
Number of stocks outstanding	95,204		95,204		109,725
1997 Stock Option Plan [Member]
Additional shares authorized for issuance			840,000
Maximum issuance of common stock	12,000,000		12,000,000
1997 Stock Option Plan [Member] | Stock Options [Member]
Number of options outstanding	224,708		224,708
1997 Stock Option Plan [Member] | Restricted Stock [Member]
Number of stocks outstanding	0		0
2007 Stock Plan [Member]
Number of options outstanding	606,447		606,447
Number of stocks outstanding	95,204		95,204
Maximum issuance of common stock	4,500,000		4,500,000
Employee Stock Purchase Plan [Member] | Common Stock [Member]
Market value of common stock on the date of grant for incentive stock options			95.00%
Maximum earnings withheld by the employees	15.00%		15.00%
Number of shares purchased under the plan			4,463	4,416
Cash received upon the issuance of common stock			$ 199,000	$ 161,000
Number of shares available for issuance	1,635,736		1,635,736
Minimum [Member]
Market value of common stock on the date of grant for incentive stock options			85.00%