Acquisition and Disposals - Catlin - Transaction related costs (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($)
Business Combination, Separately Recognized Transactions [Line Items]
Liabilities at December 31, 2016	$ 36,966
Costs incurred in 2017	33,949
2017 payments	30,000
Liabilities at March 31, 2017	40,915
Severance related costs
Business Combination, Separately Recognized Transactions [Line Items]
Liabilities at December 31, 2016	25,360
Costs incurred in 2017	13,056
2017 payments	11,263
Liabilities at March 31, 2017	27,153
Retention and other compensation costs
Business Combination, Separately Recognized Transactions [Line Items]
Liabilities at December 31, 2016	4,481
Costs incurred in 2017	6,454
2017 payments	7,373
Liabilities at March 31, 2017	3,562
Facilities-related costs
Business Combination, Separately Recognized Transactions [Line Items]
Liabilities at December 31, 2016	18
Costs incurred in 2017	4,612
2017 payments	2,168
Liabilities at March 31, 2017	2,462
Consulting and other
Business Combination, Separately Recognized Transactions [Line Items]
Liabilities at December 31, 2016	7,107
Costs incurred in 2017	9,827
2017 payments	9,196
Liabilities at March 31, 2017	$ 7,738