Guarantor Financial Information Balance Sheet (Details) - USD ($) $ in Thousands		Jun. 30, 2017		Dec. 31, 2016		Jun. 30, 2016	Dec. 31, 2015
ASSETS
Total investments available for sale		$ 32,603,118		$ 31,919,126
Total investments trading		1,772,877		1,626,577
Investments in affiliates		2,127,115		2,177,645
Other investments		1,126,741		1,164,564
Investments		37,629,851		36,887,912
Cash and cash equivalents		3,133,822		3,426,988		$ 3,316,749	$ 3,256,236
Restricted cash		181,230		153,504
Investments in subsidiaries		0		0
Accrued investment income		270,730		284,366
Deferred acquisition costs and value of business acquired		1,143,671		946,721
Ceded unearned premiums		2,566,652		1,687,864
Premiums receivable		6,973,206		5,522,976
Reinsurance balances receivable		755,511		577,479
Unpaid losses and loss expenses recoverable		5,858,369		5,491,297
Receivable from investments sold		442,339		128,411
Goodwill and other intangible assets		2,219,390		2,203,653
Deferred tax asset		293,219		310,542
Amounts due from subsidiaries/parent		0		0
Other assets		914,260		812,389
Total assets		62,382,250		58,434,102
Liabilities:
Unpaid losses and loss expenses		26,822,346		25,939,571		26,020,564	25,439,744
Deposit liabilities		1,123,628		1,116,233
Future policy benefit reserves		3,591,573		3,506,047
Funds withheld on GreyCastle life retrocession arrangements		918,304		998,968
Unearned premiums		8,848,374		7,293,028
Notes payable and debt	[1]	3,207,339		2,647,677
Reinsurance balances payable		3,428,302		2,451,717
Payable for investments purchased		268,771		226,009
Deferred tax liability		97,879		77,271
Amounts due to subsidiaries/parent		0		0
Other liabilities		973,327		1,216,902
Total liabilities		49,279,843		45,473,423
Shareholders' Equity:
Shareholders' equity attributable to XL Group Ltd		11,080,552		10,938,512
Non-controlling interest in equity of consolidated subsidiaries		2,021,855		2,022,167
Total shareholders' equity		13,102,407		12,960,679		13,663,932
Total liabilities and shareholders' equity		62,382,250		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		(174,654)	0
Restricted cash		0		0
Investments in subsidiaries		(25,713,912)		(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		(80,759)		(115,742)
Other assets		0		0
Total assets		(25,794,681)		(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		(80,759)		(115,742)
Other liabilities		0		0
Total liabilities		(80,759)		(115,742)
Shareholders' Equity:
Shareholders' equity attributable to XL Group Ltd		(25,708,412)		(25,135,893)
Non-controlling interest in equity of consolidated subsidiaries		(5,510)		(55)
Total shareholders' equity		(25,713,922)		(25,135,948)
Total liabilities and shareholders' equity		(25,794,681)		(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		1,144	[2]	1,022	[2]	13,436	11,557
Restricted cash	[2]	0		0
Investments in subsidiaries	[2]	11,068,864	[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]	14,706		42,780
Other assets	[2]	12,311		15,188
Total assets	[2]	11,097,035		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]	16,483		17,728
Total liabilities	[2]	16,483		17,728
Shareholders' Equity:
Shareholders' equity attributable to XL Group Ltd	[2]	11,080,552		10,938,512
Non-controlling interest in equity of consolidated subsidiaries	[2]	0		0
Total shareholders' equity	[2]	11,080,552		10,938,512
Total liabilities and shareholders' equity	[2]	11,097,035		10,956,240
XLIT
ASSETS
Total investments available for sale		570,576		638,236
Total investments trading		0		0
Investments in affiliates		0		0
Other investments		0		9
Investments		570,576		638,245
Cash and cash equivalents		423,398		84,286		133,711	369,997
Restricted cash		0		0
Investments in subsidiaries		14,645,048		14,238,698
Accrued investment income		2,484		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		46,375		0
Goodwill and other intangible assets		0		0
Deferred tax asset		0		0
Amounts due from subsidiaries/parent		0		0
Other assets		32,335		40,108
Total assets		15,720,216		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
Notes payable and debt		3,207,339		2,647,677
Reinsurance balances payable		0		0
Payable for investments purchased		0		0
Deferred tax liability		0		0
Amounts due to subsidiaries/parent		66,053		72,962
Other liabilities		33,460		41,984
Total liabilities		3,306,852		2,762,623
Shareholders' Equity:
Shareholders' equity attributable to XL Group Ltd		11,063,364		10,897,195
Non-controlling interest in equity of consolidated subsidiaries		1,350,000		1,344,500
Total shareholders' equity		12,413,364		12,241,695
Total liabilities and shareholders' equity		15,720,216		15,004,318
Other XL Subsidiaries
ASSETS
Total investments available for sale		32,032,542		31,280,890
Total investments trading		1,772,877		1,626,577
Investments in affiliates		2,127,115		2,177,645
Other investments		1,126,741		1,164,555
Investments		37,059,275		36,249,667
Cash and cash equivalents		2,709,280		3,341,680		$ 3,344,256	$ 2,874,682
Restricted cash		181,230		153,504
Investments in subsidiaries		0		0
Accrued investment income		268,246		281,385
Deferred acquisition costs and value of business acquired		1,143,671		946,721
Ceded unearned premiums		2,566,652		1,687,864
Premiums receivable		6,973,206		5,522,976
Reinsurance balances receivable		755,511		577,479
Unpaid losses and loss expenses recoverable		5,858,369		5,491,297
Receivable from investments sold		395,964		128,411
Goodwill and other intangible assets		2,219,390		2,203,653
Deferred tax asset		293,219		310,542
Amounts due from subsidiaries/parent		66,053		72,962
Other assets		869,614		757,093
Total assets		61,359,680		57,725,234
Liabilities:
Unpaid losses and loss expenses		26,822,346		25,939,571
Deposit liabilities		1,123,628		1,116,233
Future policy benefit reserves		3,591,573		3,506,047
Funds withheld on GreyCastle life retrocession arrangements		918,304		998,968
Unearned premiums		8,848,374		7,293,028
Notes payable and debt		0		0
Reinsurance balances payable		3,428,302		2,451,717
Payable for investments purchased		268,771		226,009
Deferred tax liability		97,879		77,271
Amounts due to subsidiaries/parent		14,706		42,780
Other liabilities		923,384		1,157,190
Total liabilities		46,037,267		42,808,814
Shareholders' Equity:
Shareholders' equity attributable to XL Group Ltd		14,645,048		14,238,698
Non-controlling interest in equity of consolidated subsidiaries		677,365		677,722
Total shareholders' equity		15,322,413		14,916,420
Total liabilities and shareholders' equity		$ 61,359,680		$ 57,725,234

[1] "In Use/Outstanding" data represent June 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 ultimately be distributed to XL Group upon completion of the liquidation.

[3] XL Group balance includes investment in $5.5 million of XLIT Series D Preference Ordinary Shares and XLIT Series E Non-Cumulative Preference Ordinary Shares.