Dispositions and Held-for-Sale (Dispositions) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Sep. 30, 2017	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Sale Leaseback Transaction [Line Items]
Proceeds from sale of business	$ 4,300
Net gain on sale of business	$ 3,800		$ 3,807	$ 0	$ 0
Impact from sale on diluted EPS (in dollars per share)	$ 0.02
Commercial Property In San Francisco
Sale Leaseback Transaction [Line Items]
Sales price		$ 120,600
Net book value		31,600
Pre-tax profit from sale		85,400
Selling costs		3,600
Current period gain recognized		71,700
Deferred gain		$ 13,700
Impact from sale on diluted EPS (in dollars per share)		$ 0.28