Commitments, Contingencies and Guarantees (Warranties) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Changes in the activity related to liability recorded in connection with representations and warranties
Reserve balance at beginning of period	$ 6,459	$ 4,048	$ 3,000
Addition of fair value of representations and warranties due to mergers and acquisitions	0	3,100	1,712
Reserve reduction	(1,095)	(580)	0
Charge-offs	(15)	(109)	(664)
Ending reserve balance	5,349	6,459	4,048
Liability for specific claims				$ 531	$ 730	$ 0
General allowance				4,818	5,729	4,048
Total reserve balance	$ 6,459	$ 4,048	$ 3,000	$ 5,349	$ 6,459	$ 4,048