Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 1	$ 1	$ 1
Common stock, shares outstanding	92,495,113	92,246,525	93,186,295