Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Fixed maturity investments trading, amortized cost	$ 8,163,962	$ 7,434,870
Preference shares, par value (in usd per share)	$ 1	$ 1
Preference shares, shares issued (in shares)	16,010,000	16,000,000
Preference shares, shares outstanding (in shares)	16,010,000	16,000,000
Common shares, par value (in usd per share)	$ 1	$ 1
Common shares, shares issued (in shares)	42,207,390	40,023,789
Common shares, shares outstanding (in shares)	42,207,390	40,023,789

Face amount or stated value per share of common stock.

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Amortized cost of investments in debt securities classified as trading.

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