Benefit Plans - Key Assumptions for Projected Benefit Obligation and Net Periodic Benefit Cost (Details)	6 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Projected benefit obligation:
Discount rate	4.20%		3.50%
Rate of compensation increase	4.30%
Net periodic benefit costs:
Discount rate	3.80%	3.50%	4.50%
Expected long-term rate of return	7.00%
Rate of compensation increase	4.03%