Segment Information (Net Premiums Earned By Geographic Region) (Details)

12 Months Ended

Dec. 31, 2016

Dec. 31, 2015

Dec. 31, 2014

Segment Reporting Information [Line Items]

Net Premiums Earned by Geographic Region

	North America		Europe(1)		Asia  Pacific/Far East		Latin America
2016	70	%	12	%	11	%	7	%
2015	60	%	15	%	15	%	10	%
2014	58	%	16	%	16	%	10	%

North America [Member]

Segment Reporting Information [Line Items]

Percentage of net premiums earned by geographic region

70.00%

60.00%

58.00%

Europe [Member]

Segment Reporting Information [Line Items]

Percentage of net premiums earned by geographic region

^[1]

12.00%

15.00%

16.00%

Asia Pacific and Far East [Member]

Segment Reporting Information [Line Items]

Percentage of net premiums earned by geographic region

11.00%

15.00%

16.00%

Latin America [Member]

Segment Reporting Information [Line Items]

Percentage of net premiums earned by geographic region

7.00%

10.00%

10.00%

[1] (1) Europe includes Eurasia and Africa region.