Stockholders' Equity (Details Textual) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Stock-Based Compensation Plan
Percentage of fair value of the common stock equal to exercise price	100.00%
Number of Matured Shares Delivered in Stock Swap Transactions	10,752	20,692	79,194
Percentage of payroll deductions	10.00%
Percentage of purchase price for stock acquired under the plan	85.00%
Number of shares issued under employee stock purchase plan	72,273	42,624	49,089
Purchase price of shares issued under employee stock purchase plan	$ 13.08	$ 25.26	$ 20.37
Net cash proceed from excise of stock options		$ 600,000	$ 1,200,000
Actual income tax benefit from excise of stock options		300,000	1,100,000
Share-based compensation expenses	10,099,000	13,795,000	12,955,000
Share-based compensation (capitalized)	5,500,000	5,200,000	4,200,000
Reduction in shares available for future grant by restricted stock	1.44
Stock Option Awards
Look back period used to estimate expected volatility of stock option grants	5 years 6 months
Remaining contract life of outstanding stock options.	5 years 4 months
Remaining contract life of exercisable stock option	4 years 8 months
Intrinsic value of exercised stock option		900,000	4,200,000
Restricted Stock Awards [Abstract]
Fair value of non-option shares granted	$ 14.86
Restricted Stock Units [Abstract]
Performance Period for RSUs		4 years 3 months	3 years 10 months
Employee Stock Ownership Plan
Minimum age to participate for ESOP	21 years
Amount contributed to ESOP	200,000	200,000	200,000
Shares of common stock contributed to ESOP	14,815	12,995	6,729
Employee Savings Plan [Abstract]
Employee Savings Plan, Employer Matching Contribution, Percent	100.00%
Employee Savings Plan, Maximum Annual Contribution Per Employee, Percent	6.00%
Employee Savings Plan, Employer Discretionary Contribution Amount	1,800,000	1,500,000	1,400,000
Employee Savings Plan, Stock Issued During Period, Shares	140,078	91,895	44,258
General and Administrative Expense [Member]
Stock-Based Compensation Plan
Share-based compensation expenses	9,300,000	12,900,000	12,200,000
Operating Lease Expense [Member]
Stock-Based Compensation Plan
Share-based compensation expenses	300,000	300,000	300,000
Employee Stock Option [Member]
Stock Option Awards
Unrecognized compensation cost related to stock options	600,000
Weighted average recognition period of cost related to stock options	6 months
Restricted Stock Awards [Member]
Stock Option Awards
Unrecognized compensation cost related to stock options	12,900,000
Weighted average recognition period of cost related to stock options	1 year 6 months
Restricted Stock Awards [Abstract]
Number of shares issued to employees, consultants and directors	869,430	543,800	499,050
Fair value of non-option shares granted	$ 14.86	$ 31.12	$ 40.28
Grant date fair value of shares vested	12,800,000	10,000,000	8,700,000
Performance Awards (RSUs) [Member]
Restricted Stock Awards [Abstract]
Number of shares issued to employees, consultants and directors	189,700
Vesting period	3 years 1 month
Fair value of non-option shares granted	$ 15.01
Restricted Stock Units [Abstract]
Performance Period for RSUs	3 years
Performance Awards (RSUs) [Member] | Performance Awards (RSU's) - Performance Condition [Member]
Stock Option Awards
Unrecognized compensation cost related to stock options	400,000
Weighted average recognition period of cost related to stock options	2 years 4 months
Restricted Stock Awards [Abstract]
Fair value of non-option shares granted	$ 15.47
Performance Awards (RSUs) [Member] | Performance Awards (RSU's) - Market Condition [Member]
Stock Option Awards
Unrecognized compensation cost related to stock options	$ 1,500,000
Restricted Stock Awards [Abstract]
Fair value of non-option shares granted	$ 14.85
Employee Stock Purchase Plan [Member]
Stock-Based Compensation Plan
Shares available for future grant under stock compensation plans	405,656
Share-Based Compensation Plan [Member]
Stock-Based Compensation Plan
Shares available for future grant under stock compensation plans	2,383,672
Minimum Payout [Member]
Restricted Stock Awards [Abstract]
Vesting period	3 years
Restricted Stock Units [Abstract]
Percent of payout for performance based restricted stock unit grants
Maximum Payout [Member]
Restricted Stock Units [Abstract]
Percent of payout for performance based restricted stock unit grants	200.00%
Employee Stock Ownership Plan
Criteria for ESOP	1 year
Target Payout [Member]
Restricted Stock Units [Abstract]
Percent of payout for performance based restricted stock unit grants	100.00%