Stock-Based Compensation Plans (Narrative) (Details)	12 Months Ended				23 Months Ended	60 Months Ended	84 Months Ended	96 Months Ended
	Dec. 31, 2020 USD ($) plan shares	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2013 shares	Dec. 31, 2020 USD ($) plan shares	Dec. 31, 2019 shares	Dec. 31, 2020 USD ($) plan shares	Dec. 31, 2020 USD ($) plan shares	Dec. 31, 2017 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, granted (in shares)	833,000	1,133,000	1,042,000
Number of shares outstanding	3,599,000	3,315,000	2,638,000		3,599,000	3,315,000	3,599,000	3,599,000	2,019,000
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares approved (in shares)				2,000,000
Shares, granted (in shares)	208,273	173,013	177,846					1,354,129
ESPP discount rate				85.00%
Discount recognized as compensation expense				15.00%
Stock Compensation Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of plans | plan	2				2		2	2
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of plans | plan	2				2		2	2
Stock option expense | $	$ 4,935,527	$ 6,345,147	$ 8,582,489
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost | $	6,062,139				$ 6,062,139		$ 6,062,139	$ 6,062,139
Shares, granted (in shares)			0
Amortization expense | $	$ 4,424,678	$ 897,136	$ 0
Number of shares outstanding			0
Omnibus Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares approved (in shares)		45,000,000				45,000,000
Shares issued under plan (in shares)	9,868,580				9,868,580		9,868,580	9,868,580
Options granted net of shares from canceled/expired options (in shares)					2,212,301
Restricted period, maximum, in years	10 years
Shares, granted (in shares)					1,603,118
Shares outstanding	3,598,778
Omnibus Incentive Plan | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option vesting period	1 year
Award expiration period	5 years
Omnibus Incentive Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option vesting period	5 years
Award expiration period	10 years
Employee Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares approved (in shares)	24,000,000				24,000,000		24,000,000	24,000,000
Options granted net of shares from canceled/expired options (in shares)							12,778,967
Unrecognized compensation cost | $	$ 7,220,109				$ 7,220,109		$ 7,220,109	$ 7,220,109
Weighted-average period for unrecognized compensation cost expected to be recognized	2 years 18 days
Restricted Stock Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares approved (in shares)	9,000,000				9,000,000		9,000,000	9,000,000
Shares, granted (in shares)						5,688,309
Unearned stock-based compensation | $	$ 39,291,347				$ 39,291,347		$ 39,291,347	$ 39,291,347
Amortization expense | $	$ 20,675,447	$ 13,770,917	$ 8,841,985