12. Equity Compensation Plan Summary of Exercisable Stock Options (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Equity Compensation Plan [Line Items]
Options Exercisable, beginning balance	1,191,441	1,290,530	1,415,799
Vested	38,771	263,553	381,787
Exercised	(478,733)	(362,642)	(507,056)
Options Exercisable, ending balance	751,479	1,191,441	1,290,530
Weighted Average Grant Date Fair Value, Exercisable at beginning balance	$ 5.41	$ 5.74	$ 4.81
Weighted Average Grant Date Fair Value, Vested	4.75	5.10	6.28
Weighted Average Grant Date Fair Value, Exercised	6.46	6.34	3.54
Weighted Average Grant Date Fair Value, Exercisable at ending balance	$ 4.71	$ 5.41	$ 5.74
Intrinsic Value	$ 21.1	$ 16.3	$ 19.3
Weighted Average Exercise Price	$ 15.83	$ 18.14	$ 18.27
Weighted Average Remaining Contractual Term	3 years 219 days	4 years 329 days	5 years 292 days