Stock-Based Compensation (Additional Information) (Details) (USD $)	6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended			6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended				6 Months Ended
	Jun. 30, 2014 offering_periods	Jun. 30, 2013	Jun. 30, 2014 Employee Stock Purchase Plan [Member]	Jun. 30, 2013 Employee Stock Purchase Plan [Member]	Jun. 30, 2014 Employee Stock Purchase Plan [Member]	Jun. 30, 2013 Employee Stock Purchase Plan [Member]	Jun. 30, 2014 Stock Options [Member]	Jun. 30, 2013 Stock Options [Member]	Jun. 30, 2014 Stock Options [Member]	Jun. 30, 2013 Stock Options [Member]	Jun. 30, 2014 Performance-Based Restricted Stock [Member]	Jun. 30, 2013 Performance-Based Restricted Stock [Member]	Jun. 30, 2014 Performance-Based Restricted Stock [Member]	Jun. 30, 2013 Performance-Based Restricted Stock [Member]	Dec. 31, 2013 Performance-Based Restricted Stock [Member]	Jun. 30, 2014 Performance-Based Restricted Stock [Member] Minimum [Member]	Jun. 30, 2014 Performance-Based Restricted Stock [Member] Maximum [Member]	Jun. 30, 2014 Time Based Restricted Stock [Member]	Jun. 30, 2013 Time Based Restricted Stock [Member]	Jun. 30, 2014 Time Based Restricted Stock [Member]	Jun. 30, 2013 Time Based Restricted Stock [Member]	Jun. 30, 2014 Deferred Stock Units [Member]	Mar. 31, 2014 Deferred Stock Units [Member]	Jun. 30, 2013 Deferred Stock Units [Member]	Mar. 31, 2013 Deferred Stock Units [Member]	Jun. 30, 2014 Deferred Stock Units [Member]	Jun. 30, 2013 Deferred Stock Units [Member]
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Stock options, contractual term (years)									10 years
Stock-based compensation, approximate forfeitures rate (percent)									3.00%				7.00%							7.00%
Compensation expense (income)	$ 4,576,000	$ 2,245,000	$ 100,000	$ 100,000	$ 200,000	$ 200,000	$ 100,000	$ 200,000	$ 200,000	$ 600,000	$ 700,000	$ 200,000	$ 1,300,000	$ 200,000				$ 1,100,000	$ 300,000	$ 2,100,000	$ 600,000	$ 800,000	$ 0	$ 700,000	$ 0	$ 800,000	$ 700,000
Options exercised, total intrinsic value	5,400,000
Total amount of cash received from exercise of options	$ 14,100,000
Restricted stock award program, measurement period (years)													3 years
Restricted stock award program, awarded shares as a percentage of the original award amount (percent)																0.00%	200.00%
Expected dividend yield (percent)													0.00%	0.00%
Restricted stock award program, payment of award as percentage of target (percent)															108.30%
Restricted stock award program, vesting period (years)																				3 years
Employee stock purchase plan, number of offering (offering period)	2
Employee stock purchase plan, offering period (months)	6 months
Employee stock purchase plan, purchase price discount (percent)					15.00%