Guarantor Financial Information Balance Sheet (Details) - USD ($) $ in Thousands		Sep. 30, 2017		Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
ASSETS
Total investments available for sale		$ 33,023,505		$ 31,919,126
Total investments trading		1,875,826		1,626,577
Investments in affiliates		2,100,378		2,177,645
Other investments		1,145,588		1,164,564
Investments		38,145,297		36,887,912
Cash and cash equivalents		3,030,088		3,426,988	$ 3,393,277	$ 3,256,236
Restricted cash		159,627		153,504
Investments in subsidiaries		0		0
Accrued investment income		270,211		284,366
Deferred acquisition costs and value of business acquired		1,073,343		946,721
Ceded unearned premiums		2,311,619		1,687,864
Premiums receivable		7,078,700		5,522,976
Reinsurance balances receivable		1,079,821		577,479
Unpaid losses and loss expenses recoverable		6,962,787		5,491,297
Receivable from investments sold		195,837		128,411
Goodwill and other intangible assets		2,227,014		2,203,653
Deferred tax asset		301,322		310,542
Amounts due from subsidiaries/parent		0		0
Other assets		954,542		812,389
Total assets		63,790,208		58,434,102
Liabilities:
Unpaid losses and loss expenses		29,988,337		25,939,571	26,170,383	25,439,744
Deposit liabilities		1,030,290		1,116,233
Future policy benefit reserves		3,656,859		3,506,047
Funds withheld on GreyCastle life retrocession arrangements		920,571		998,968
Unearned premiums		8,344,536		7,293,028
Notes payable and debt	[1]	3,210,063		2,647,677
Reinsurance balances payable		3,706,120		2,451,717
Payable for investments purchased		273,449		226,009
Deferred tax liability		107,157		77,271
Amounts due to subsidiaries/parent		0		0
Other liabilities		1,024,316		1,216,902
Total liabilities		52,261,698		45,473,423
Shareholders' Equity:
Shareholders' equity attributable to XL Group Ltd		9,939,847		10,938,512
Non-controlling interest in equity of consolidated subsidiaries		1,588,663		2,022,167
Total shareholders' equity		11,528,510		12,960,679	13,592,880
Total liabilities and shareholders' equity		63,790,208		58,434,102
Consolidating Adjustments and Eliminations
ASSETS
Total investments available for sale		0		0
Total investments trading		0		0
Investments in affiliates		0		0
Other investments		0		0
Investments		0		0
Cash and cash equivalents		0		0	0	0
Restricted cash		0		0
Investments in subsidiaries		(23,256,516)		(25,135,893)
Accrued investment income		(10)		(55)
Deferred acquisition costs and value of business acquired		0		0
Ceded unearned premiums		0		0
Premiums receivable		0		0
Reinsurance balances receivable		0		0
Unpaid losses and loss expenses recoverable		0		0
Receivable from investments sold		0		0
Goodwill and other intangible assets		0		0
Deferred tax asset		0		0
Amounts due from subsidiaries/parent		(107,663)		(115,742)
Other assets		0		0
Total assets		(23,364,189)		(25,251,690)
Liabilities:
Unpaid losses and loss expenses		0		0
Deposit liabilities		0		0
Future policy benefit reserves		0		0
Funds withheld on GreyCastle life retrocession arrangements		0		0
Unearned premiums		0		0
Notes payable and debt		0		0
Reinsurance balances payable		0		0
Payable for investments purchased		0		0
Deferred tax liability		0		0
Amounts due to subsidiaries/parent		(107,663)		(115,742)
Other liabilities		0		0
Total liabilities		(107,663)		(115,742)
Shareholders' Equity:
Shareholders' equity attributable to XL Group Ltd		(23,256,016)		(25,135,893)
Non-controlling interest in equity of consolidated subsidiaries		(510)		(55)
Total shareholders' equity		(23,256,526)		(25,135,948)
Total liabilities and shareholders' equity		(23,364,189)		(25,251,690)
XL- Bermuda/Ireland
ASSETS
Total investments available for sale	[2]	0		0
Total investments trading	[2]	0		0
Investments in affiliates	[2]	0		0
Other investments	[2]	0		0
Investments	[2]	0		0
Cash and cash equivalents	[2]	3,531		1,022	12,875	11,557
Restricted cash	[2]	0		0
Investments in subsidiaries	[2]	9,905,108	[3]	10,897,195
Accrued investment income	[2]	10		55
Deferred acquisition costs and value of business acquired	[2]	0		0
Ceded unearned premiums	[2]	0		0
Premiums receivable	[2]	0		0
Reinsurance balances receivable	[2]	0		0
Unpaid losses and loss expenses recoverable	[2]	0		0
Receivable from investments sold	[2]	0		0
Goodwill and other intangible assets	[2]	0		0
Deferred tax asset	[2]	0		0
Amounts due from subsidiaries/parent	[2]	39,908		42,780
Other assets	[2]	14,454		15,188
Total assets	[2]	9,963,011		10,956,240
Liabilities:
Unpaid losses and loss expenses	[2]	0		0
Deposit liabilities	[2]	0		0
Future policy benefit reserves	[2]	0		0
Funds withheld on GreyCastle life retrocession arrangements	[2]	0		0
Unearned premiums	[2]	0		0
Notes payable and debt	[2]	0		0
Reinsurance balances payable	[2]	0		0
Payable for investments purchased	[2]	0		0
Deferred tax liability	[2]	0		0
Amounts due to subsidiaries/parent	[2]	0		0
Other liabilities	[2]	23,164		17,728
Total liabilities	[2]	23,164		17,728
Shareholders' Equity:
Shareholders' equity attributable to XL Group Ltd	[2]	9,939,847		10,938,512
Non-controlling interest in equity of consolidated subsidiaries	[2]	0		0
Total shareholders' equity	[2]	9,939,847		10,938,512
Total liabilities and shareholders' equity	[2]	9,963,011		10,956,240
XLIT
ASSETS
Total investments available for sale		525,675		638,236
Total investments trading		0		0
Investments in affiliates		0		0
Other investments		0		9
Investments		525,675		638,245
Cash and cash equivalents		265,369		84,286	14,495	369,997
Restricted cash		0		0
Investments in subsidiaries		13,351,408		14,238,698
Accrued investment income		2,291		2,981
Deferred acquisition costs and value of business acquired		0		0
Ceded unearned premiums		0		0
Premiums receivable		0		0
Reinsurance balances receivable		0		0
Unpaid losses and loss expenses recoverable		0		0
Receivable from investments sold		0		0
Goodwill and other intangible assets		0		0
Deferred tax asset		0		0
Amounts due from subsidiaries/parent		0		0
Other assets		32,151		40,108
Total assets		14,176,894		15,004,318
Liabilities:
Unpaid losses and loss expenses		0		0
Deposit liabilities		0		0
Future policy benefit reserves		0		0
Funds withheld on GreyCastle life retrocession arrangements		0		0
Unearned premiums		0		0
Notes payable and debt		3,210,063		2,647,677
Reinsurance balances payable		0		0
Payable for investments purchased		1,252		0
Deferred tax liability		0		0
Amounts due to subsidiaries/parent		67,765		72,962
Other liabilities		35,785		41,984
Total liabilities		3,314,865		2,762,623
Shareholders' Equity:
Shareholders' equity attributable to XL Group Ltd		9,904,608		10,897,195
Non-controlling interest in equity of consolidated subsidiaries		957,421		1,344,500
Total shareholders' equity		10,862,029		12,241,695
Total liabilities and shareholders' equity		14,176,894		15,004,318
Other XL Subsidiaries
ASSETS
Total investments available for sale		32,497,830		31,280,890
Total investments trading		1,875,826		1,626,577
Investments in affiliates		2,100,378		2,177,645
Other investments		1,145,588		1,164,555
Investments		37,619,622		36,249,667
Cash and cash equivalents		2,761,188		3,341,680	$ 3,365,907	$ 2,874,682
Restricted cash		159,627		153,504
Investments in subsidiaries		0		0
Accrued investment income		267,920		281,385
Deferred acquisition costs and value of business acquired		1,073,343		946,721
Ceded unearned premiums		2,311,619		1,687,864
Premiums receivable		7,078,700		5,522,976
Reinsurance balances receivable		1,079,821		577,479
Unpaid losses and loss expenses recoverable		6,962,787		5,491,297
Receivable from investments sold		195,837		128,411
Goodwill and other intangible assets		2,227,014		2,203,653
Deferred tax asset		301,322		310,542
Amounts due from subsidiaries/parent		67,755		72,962
Other assets		907,937		757,093
Total assets		63,014,492		57,725,234
Liabilities:
Unpaid losses and loss expenses		29,988,337		25,939,571
Deposit liabilities		1,030,290		1,116,233
Future policy benefit reserves		3,656,859		3,506,047
Funds withheld on GreyCastle life retrocession arrangements		920,571		998,968
Unearned premiums		8,344,536		7,293,028
Notes payable and debt		0		0
Reinsurance balances payable		3,706,120		2,451,717
Payable for investments purchased		272,197		226,009
Deferred tax liability		107,157		77,271
Amounts due to subsidiaries/parent		39,898		42,780
Other liabilities		965,367		1,157,190
Total liabilities		49,031,332		42,808,814
Shareholders' Equity:
Shareholders' equity attributable to XL Group Ltd		13,351,408		14,238,698
Non-controlling interest in equity of consolidated subsidiaries		631,752		677,722
Total shareholders' equity		13,983,160		14,916,420
Total liabilities and shareholders' equity		$ 63,014,492		$ 57,725,234

[1] "In Use/Outstanding" data represent September 30, 2017 and December 31, 2016 accreted values.

[2] Results for the period include XL-Ireland, which prior to the Redomestication was the ultimate parent and is now in liquidation proceedings as outlined in Note 1, "Significant Accounting Policies." The Company expects the net assets of XL-Ireland to be distributed to XL Group upon completion of the liquidation.

[3] XL Group balance includes investment in $0.5 million of XLIT Series E Non-Cumulative Preference Ordinary Shares.