Stock-Based Compensation Plans (Narrative) (Details)			12 Months Ended
	Dec. 31, 2014	Dec. 05, 2014	Dec. 31, 2015 USD ($) plan $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2013 USD ($) $ / shares shares	May. 31, 2014 shares	Dec. 31, 2012 shares	Dec. 31, 2003 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares sold to employees during period			201,785	137,028	155,264
Shares granted with restriction period			229,660	431,880	374,180
Employee Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options available for grant (up to)						24,000,000
Options granted net of shares from canceled/expired options			7,472,734
Unrecognized compensation cost | $			$ 20,728,349
Weighted-average period for unrecognized compensation cost expected to be recognized			2 years
Non-Employee Director Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option vesting period			6 months
Shares approved							1,000,000
Grants in period (in shares)			1,086,480
Option expiration period, years			10 years
Previous Non-Employee Director Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (in shares)			315,000
Restricted Stock Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares approved			9,000,000
Restricted period, maximum, in years			10 years
Shares granted with restriction period			1,530,380
Restricted period for granted shares, in years			5 years
Unearned stock-based compensation | $			$ 11,536,022
Amortization expense | $			$ 3,486,242	$ 3,095,136	$ 2,760,446
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares approved								2,000,000
ESPP discount rate			85.00%
Discount recognized as compensation expense				15.00%
Employee Stock Purchase Plan, 2003
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares sold to employees during period			0	0	52,340
Cumulative shares sold to employees during period			2,400,000
Weighted average fair value of shares sold | $ / shares			$ 8.51
Employee Stock Purchase Plan, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares sold to employees during period			201,785	137,028	102,924
Cumulative shares sold to employees during period			441,737
Weighted average fair value of shares sold | $ / shares			$ 14.11
Minimum | Employee Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option vesting period			1 year
Award expiration period			5 years
Minimum | Restricted Stock Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Market price | $ / shares			$ 15.50	$ 13.39	$ 10.12
Maximum | Employee Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option vesting period			5 years
Award expiration period			7 years
Maximum | Restricted Stock Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Market price | $ / shares			$ 18.30	$ 18.31	$ 16.42
Stock Compensation Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of plans | plan			4
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of plans | plan			2
Common Stocks
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock split conversion ratio	2	2