Stock Options And Employee Stock Purchase Plan (Narrative) (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Allocated Share-based Compensation Expense	$ 1,963,000	$ 2,335,000	$ 4,347,000	$ 4,683,000
Number of options outstanding	791,771		791,771		1,175,657
Number of options granted			0
Cash received upon the issuance of common stock			123,000	106,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Total Intrinsic Value			12,800,000	4,000,000
Stock Options [Member]
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	1,300,000		1,300,000		2,000,000
Restricted Stock And Restricted Stock Unit (RSU) [Member]
Allocated Share-based Compensation Expense			3,600,000	3,200,000
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	24,800,000		24,800,000		20,200,000
Restricted Stock [Member]
Shares, Granted			176,864
Weighted-Average Grant-Date Fair Value, Granted			$ 44.65
Number of stocks outstanding	934,191		934,191		1,178,371
Restricted Stock Units (RSUs) [Member]
Shares, Granted			16,737
Number of stocks outstanding	100,604		100,604		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	238,429		238,429
1997 Stock Option Plan [Member] | Restricted Stock [Member]
Number of stocks outstanding	0		0
2007 Stock Plan [Member]
Number of options outstanding	653,946		653,946
Number of stocks outstanding	100,604		100,604
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			2,824	3,158
Cash received upon the issuance of common stock			$ 123,000	$ 106,000
Number of shares available for issuance	1,637,375		1,637,375
Minimum [Member]
Market value of common stock on the date of grant for incentive stock options			85.00%