Share-Based Compensation - Stock Option Activity under Stock Option Plans (Details) (USD $)	6 Months Ended
	Jun. 30, 2014
Number of Shares
Beginning balance (in shares)	958,786
Granted (in shares)
Exercised (in shares)	(38,650)
Cancelled (in shares)	(68,707)
Ending balance (in shares)	851,429
Vested and Expected to Vest (in shares)	851,429
Exercisable (in shares)	842,429
Weighted-Average Exercise Price
Beginning balance (in dollars per share)	$ 21.32
Granted (in dollars per share)
Exercised (in dollars per share)	$ 11.64
Cancelled (in dollars per share)	$ 22.55
Ending balance (in dollars per share)	$ 21.65
Vested and Expected to Vest (in dollars per share)	$ 21.65
Exercisable (in dollars per share)	$ 21.72
Weighted Average Remaining Contractual Term
Outstanding	3 years 5 months 16 days
Vested and Expected to Vest	2 years 11 months 12 days
Exercisable	3 years 4 months 21 days
Aggregate Intrinsic Value
Outstanding	$ 2,149,732
Vested and Expected to Vest	2,149,732
Exercisable	$ 2,097,352