Stock Options And Employee Stock Purchase Plan (Narrative) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Allocated Share-based Compensation Expense	$ 3,168,000	$ 1,963,000	$ 6,173,000	$ 4,347,000
Number of options outstanding	659,811		659,811		725,649
Number of options granted			62,000
Cash received upon the issuance of common stock			$ 126,000	123,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Total Intrinsic Value			5,600,000	12,800,000
Stock Options [Member]
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	$ 1,400,000		1,400,000		$ 800,000
Restricted Stock And Restricted Stock Unit (RSU) [Member]
Allocated Share-based Compensation Expense			5,700,000	$ 3,600,000
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	$ 33,900,000		$ 33,900,000		$ 24,100,000
Restricted Stock [Member]
Shares, Granted			147,440
Weighted-Average Grant-Date Fair Value, Granted			$ 66.04
Number of stocks outstanding	762,292		762,292		814,050
Restricted Stock Units (RSUs) [Member]
Shares, Granted			10,900
Number of stocks outstanding	92,953		92,953		102,924
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	125,498		125,498
1997 Stock Option Plan [Member] | Restricted Stock [Member]
Number of stocks outstanding	0		0
2007 Stock Plan [Member]
Number of options outstanding	472,313		472,313
Number of stocks outstanding	92,953		92,953
Maximum issuance of common stock	4,500,000		4,500,000
2015 Stock Option Plan [Member]
Number of options outstanding	62,000		62,000
Number of stocks outstanding	0		0
Maximum issuance of common stock	4,200,000		4,200,000
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			2,104	2,824
Cash received upon the issuance of common stock			$ 126,000	$ 123,000
Number of shares available for issuance	1,632,360		1,632,360
Minimum [Member]
Market value of common stock on the date of grant for incentive stock options			85.00%