Stock Incentive Plans (Details Textual) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Stock Incentive Plans [Line Items]
Number of common stock authorized for Long-Term Incentive Plan	6,200,000
Stock-based compensation expense	$ 9,054,000	$ 7,667,000
Maximum [Member]
Stock Incentive Plans [Line Items]
Vesting period	5 years
Minimum [Member]
Stock Incentive Plans [Line Items]
Vesting period	3 years
Employee Stock Option [Member] | Employee Stock Option [Member]
Stock Incentive Plans [Line Items]
Vesting period	10 years
Employee Stock Option [Member] | Employee Stock Option [Member] | Director [Member]
Stock Incentive Plans [Line Items]
Vesting period	3 years
Employee Stock Option [Member] | Employee Stock Option [Member] | Officer [Member]
Stock Incentive Plans [Line Items]
Vesting period	5 years