Share-Based Compensation - Stock Option Activity under Stock Option Plans (Details) (USD $)	3 Months Ended
	Mar. 31, 2015
Number of Shares
Beginning balance (in shares)	737,931
Granted (in shares)
Exercised (in shares)	(23,373)
Cancelled (in shares)	(100)
Ending balance (in shares)	714,458
Vested and Expected to Vest (in shares)	714,458
Exercisable (in shares)	714,458
Weighted-Average Exercise Price
Beginning balance (in dollars per share)	$ 20.99
Granted (in dollars per share)
Exercised (in dollars per share)	$ 15.17
Cancelled (in dollars per share)	$ 28.25
Ending balance (in dollars per share)	$ 21.18
Vested and Expected to Vest (in dollars per share)	$ 21.18
Exercisable (in dollars per share)	$ 21.18
Weighted Average Remaining Contractual Term
Outstanding	2 years 10 months 4 days
Vested and Expected to Vest	2 years 10 months 4 days
Exercisable	2 years 10 months 4 days
Aggregate Intrinsic Value
Outstanding	$ 2,742,203
Vested and Expected to Vest	2,742,203
Exercisable	$ 2,742,203