Commitments and Contingencies, Variable Interest Entities (Details) - Low-Income Housing Limited Partnerships - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Amount Reflected in Consolidated Balance Sheets [Abstract]
Current assets	$ 375	$ 377
Property, plant and equipment, net	2,025	2,199
Other noncurrent assets	125	127
Total assets	2,525	2,703
Current liabilities	1,269	1,246
Mortgages and other long-term debt payable	486	537
Other noncurrent liabilities	54	51
Total liabilities	$ 1,809	$ 1,834