CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Jun. 30, 2013
Statement of Financial Position [Abstract]
Fixed maturities, amortized cost	$ 4,684,148	$ 4,602,514
Shareholders' equity
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares authorized (in shares)	1,000,000,000	1,000,000,000	680,000,000
Common stock, shares issued (in shares)	340,097,000	340,047,000
Common stock, shares outstanding (in shares)	339,657,000	338,560,000
Treasury stock, shares at cost (in shares)	440,000	1,487,000