Significant Accounting Policies Share-Based Compensation (Details)	12 Months Ended
	Dec. 31, 2016
Stock Options [Member]
Share-based Compensation Arrangements by Share-based Payment Award [Line Items]
Vesting period (in years)	7 years
Prior to 2013 [Member] | Non-vested Common Stock [Member]
Share-based Compensation Arrangements by Share-based Payment Award [Line Items]
Vesting period (in years)	5 years
2013 and Beyond Plan [Member] | Non-vested Common Stock [Member]
Share-based Compensation Arrangements by Share-based Payment Award [Line Items]
Vesting period (in years)	3 years
Share-based Compensation Arrangement by Share-based Payment Award, Award Required Holding Period	2 years