Benefit Plans Long-Term Incentive Plan (Details) - shares	12 Months Ended
	Dec. 31, 2015	May. 31, 2015	May. 31, 2014	May. 31, 2004
2004 Long-Term Incentive Plan
Share based plans
Shares authorized				525,500
Term of plan (in years)	10 years
Vesting percentage per year	33.30%
Number of options outstanding (in shares)	318,355
Granted (in shares)	0
2012 Plan
Share based plans
Shares authorized		620,000	800,000
Term of plan (in years)	10 years
Vesting percentage per year	33.30%
Number of options outstanding (in shares)	740,731
Granted (in shares)	816,105
2014 Plan
Share based plans
Shares authorized			1,420,000