Taxation - Reconciliation of effective tax rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Expected tax provision at weighted average rate	$ (31,080)	$ (50,797)	$ 132,775
Permanent differences:
Non taxable (income) loss	(19,937)	(23,036)	(19,870)
Revision to prior year estimates	(24,121)	7,402	2,016
State, local and foreign taxes	23,157	27,499	47,078
Valuation allowance	1,197	9,517	(181)
Net allocated investment income	5,990	(405)	3,399
Stock awards	543	(433)	411
Non-deductible expenses	48,206	42,839	22,556
Realized capital loss carry-forward valuation allowance reduction	(905)	2,075	(2,916)
Adjustments related to Life Retro Arrangements	21,682	(35,045)	(99,535)
Non-taxable reserve release	(6,233)	(11,877)	3,974
Uncertain tax positions	23,630	13,100	7,190
Total tax expense	$ 42,129	$ (19,161)	$ 96,897