Pension Plans - Contributions (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Qualified Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Contributions paid-to-date	$ 10,000,000	$ 10,000,000
Expected future contributions	0
Supplemental Employee Retirement Plans [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans
Contributions paid-to-date	400,000	$ 500,000
SERP, Expected contributions	$ 100,000