Stock-Based Compensation Plans (Narrative) (Details)			12 Months Ended
	Dec. 31, 2014	Dec. 05, 2014	Dec. 31, 2016 USD ($) plan $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 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]
Unrecognized compensation cost | $			$ 0
Shares granted with restriction period (in shares)			246,660	229,660	431,880
Employee Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options available for grant (in shares)						24,000,000
Options granted net of shares from canceled/expired options (in shares)			10,342,260
Unrecognized compensation cost | $			$ 17,732,000
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 (in shares)							1,000,000
Grants in period (in shares)			1,074,480
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)			371,000
Restricted Stock Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares approved (in shares)				9,000,000
Restricted period, maximum, in years				10 years
Shares granted with restriction period (in shares)			1,532,480
Shares, Granted (in shares)			4,477,580
Restricted period for granted shares, in years			5 years
Unearned stock-based compensation | $			$ 11,063,638
Amortization expense | $			$ 3,885,042	$ 3,486,242	$ 3,095,136
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares approved (in shares)								2,000,000
ESPP discount rate			85.00%
Discount recognized as compensation expense				15.00%
Employee Stock Purchase Plan, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares sold to employees during period (in shares)			177,781	201,785	137,028
Cumulative shares sold to employees during period (in shares)			619,518
Weighted average fair value of shares sold (in dollars per share) | $ / shares			$ 14.24
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 (in dollars per share) | $ / shares			$ 14.70	$ 15.50	$ 13.39
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 (in dollars per share) | $ / shares			$ 19.69	$ 18.30	$ 18.31
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
Common stock split, stock dividend percent	100.00%	100.00%