Unaudited Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Mar. 31, 2020		Dec. 31, 2019
Fixed maturities available for sale, at amortized cost	$ 16,757,086		$ 16,598,808
Allowance for credit losses on investments	9,938		0
Short-term investments available for sale, at amortized cost	944,878		957,283
Collateral received under securities lending, at amortized cost	182,274		388,366
Securities pledged under securities lending, at amortized cost	175,218		378,738
Allowance for credit losses on premiums receivable	27,990		21,003
Allowance for credit losses on reinsurance recoverable	13,700		1,364
Allowance for credit losses on contractholder receivable	$ 9,038		$ 0
Common shares, par value per share	$ 0.0011		$ 0.0011
Common shares issued (shares)	577,386,799		574,617,195
Common shares held in treasury (shares)	171,776,932		168,997,994
Fixed maturities
Allowance for credit losses on investments	$ 9,909		$ 0
Short-term investments
Allowance for credit losses on investments	29	[1]	0
Short-term investments available for sale, at amortized cost	$ 944,878		$ 957,283

[1] Effective January 1, 2020, the Company adopted ASU 2016-13 and as a result any credit impairment losses on the Company’s available-for-sale investments are recorded as an allowance, subject to reversal.