Real Estate Charges - Activity in the Liability Account Relating to Office Space Consolidation Initiatives (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Real estate liability restructuring reserve [Abstract]
Balance as of January 1,	$ 116,064	$ 148,429
(Credit) expense incurred	(2,874)	2,258
Payments made	(25,829)	(38,920)
Interest accretion	4,293	4,297
Balance as of end of period	$ 91,654	$ 116,064