Share-Based Compensation - Stock Option Activity under Stock Option Plans (Details) (USD $)	3 Months Ended
	Mar. 31, 2014
Number of Shares
Beginning balance (in shares)	958,786
Granted (in shares)
Exercised (in shares)	(25,050)
Cancelled (in shares)	1,815
Ending balance (in shares)	935,551
Vested and Expected to Vest (in shares)	935,551
Exercisable (in shares)	926,551
Weighted-Average Exercise Price
Beginning balance (in dollars per share)	$ 21.32
Granted (in dollars per share)
Exercised (in dollars per share)	$ 10.88
Cancelled (in dollars per share)	$ 22.15
Ending balance (in dollars per share)	$ 21.60
Vested and Expected to Vest (in dollars per share)	$ 21.60
Exercisable (in dollars per share)	$ 21.66
Weighted Average Remaining Contractual Term
Outstanding	2 years 11 months 19 days
Vested and Expected to Vest	2 years 11 months 19 days
Exercisable	2 years 10 months 28 days
Aggregate Intrinsic Value
Outstanding	$ 2,401,422
Vested and Expected to Vest	2,401,422
Exercisable	$ 2,344,542