Stockholders' Equity (Narrative) (Details) (USD $)	3 Months Ended	9 Months Ended			9 Months Ended			1 Months Ended		9 Months Ended					12 Months Ended
	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Oct. 31, 2011	Sep. 30, 2013 Stock Options [Member]	Sep. 30, 2012 Stock Options [Member]	Sep. 30, 2013 Restricted Stock [Member]	May 31, 2012 2002 Stock Incentive Plan [Member]	Sep. 30, 2013 2002 Stock Incentive Plan [Member] Stock Options [Member]	Sep. 30, 2013 Employee Stock Purchase Plan [Member]	Sep. 30, 2012 Employee Stock Purchase Plan [Member]	Sep. 30, 2013 Employee Stock Purchase Plan [Member] Stock Options [Member]	Sep. 30, 2012 Employee Stock Purchase Plan [Member] Stock Options [Member]	Sep. 30, 2013 ATM [Member]	Dec. 31, 2012 ATM [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase the number of shares under the 2002 Stock Incentive Plan								1,800,000
Weighted-average grant date fair value of stock options					$ 14.28
Intrinsic value of options exercised					$ 3,600,000	$ 300,000
Unrecognized compensation cost					8,100,000
Weighted-average period in which cost is expected to be recognized					2 years 5 months 27 days		1 year 4 months 28 days
Net proceeds from employee stock purchase plan		84,000	68,000									3,000,000	500,000
Shares available for future option grants									1,500,000
Unrecognized compensation cost, restricted stock							1,700,000
Employee Stock Purchase Plan
Shares allowed to purchase in employee stock purchase plan										1,250
Offering period of shares in employee stock purchase plan										6 months
Percentage of purchase price of stock										85.00%
Discount rate										15.00%
Shares issued in period										5,016	7,374
Stock-based compensation expense		4,149,000	3,116,000							37,000	29,000
Shares available for future purchases										81,512
Public Offering
Equity, reserved for issuance		30,000,000		30,000,000
Stock issued, shares	150,000		150,000											302,750
Net proceeds from issuance of common stock	2,600,000		2,647,000											5,500,000	30,000,000
Weighted average price	$ 18.19		$ 18.19
Corporate Share Repurchase
Stock repurchase, authorized amount		$ 5,000,000
Stock repurchase, maximum period		1 year