Employee Benefit Plans (Narrative) (Details) (USD $)	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended			3 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 Restricted Stock Units	Jun. 30, 2013 Restricted Stock Units	Jun. 30, 2014 Restricted Stock Units	Jun. 30, 2013 Restricted Stock Units	Jun. 30, 2014 Restricted Stock Units Service-Based Awards [Member]	Jun. 30, 2014 Restricted Stock Units Performance Based Awards [Member]	Mar. 31, 2014 Restricted Stock Units Performance Based Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost related to unvested restricted stock units	$ 21,100,000		$ 21,100,000
Total unrecognized compensation cost, weighted- average period of recognition			3 years 3 months 11 days				2 years 3 months 26 days
Award vesting period									4 years
Restricted stock units vesting percentage after one year									25.00%
Granted							330,000			199,000	106,500
Maximum percentage of performance-based restricted stock units											150.00%
Stock-based compensation expense	4,240,000	2,485,000	6,278,000	3,558,000	2,700,000	700,000	3,500,000	900,000
Total unrecognized compensation cost related to unvested stock options					$ 23,800,000		$ 23,800,000