Fair Value Measurements (Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Level 3 Inputs) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of the period	$ 1,719	$ 6,726
Total unrealized gains (losses)
Included in net investment income	(118)	(359)
Included in other income (loss)		(426)
Total realized gains (losses)
Included in other income (loss)	6,339	6,628
Total foreign exchange gains		7
Purchases	(13,444)	(80,996)
Sales		(84,353)
Settlements	(7,500)	(7,500)
Balance at end of the period	(13,004)	1,719
Net investment income
Total realized gains (losses)
Change in unrealized gains for the period included in earnings for assets held at the end of the period		(359)
Other income (loss)
Total realized gains (losses)
Change in unrealized gains for the period included in earnings for assets held at the end of the period		(426)
Fixed maturity investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of the period	7,618	15,660
Total unrealized gains (losses)
Included in net investment income	(118)	(542)
Included in other income (loss)		0
Total realized gains (losses)
Included in other income (loss)	0	0
Total foreign exchange gains		0
Purchases	0	0
Sales		0
Settlements	(7,500)	(7,500)
Balance at end of the period	0	7,618
Fixed maturity investments | Net investment income
Total realized gains (losses)
Change in unrealized gains for the period included in earnings for assets held at the end of the period		(359)
Fixed maturity investments | Other income (loss)
Total realized gains (losses)
Change in unrealized gains for the period included in earnings for assets held at the end of the period		0
Other assets and (liabilities)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of the period	(5,899)	(8,934)
Total unrealized gains (losses)
Included in net investment income	0	183
Included in other income (loss)		(426)
Total realized gains (losses)
Included in other income (loss)	6,339	6,628
Total foreign exchange gains		7
Purchases	(13,444)	(80,996)
Sales		(84,353)
Settlements	0	0
Balance at end of the period	$ (13,004)	(5,899)
Other assets and (liabilities) | Net investment income
Total realized gains (losses)
Change in unrealized gains for the period included in earnings for assets held at the end of the period		0
Other assets and (liabilities) | Other income (loss)
Total realized gains (losses)
Change in unrealized gains for the period included in earnings for assets held at the end of the period		$ (426)