Real Estate Charges (Details) $ in Thousands, ft² in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2017 USD ($) ft²	Dec. 31, 2016 USD ($)
Restructuring and Related Activities [Abstract]
Square feet of office space sub-leased | ft²	1
Real estate liability restructuring reserve [Abstract]
Balance as of beginning of period	$ 112,932	$ 123,912
Expense (credit) incurred	15,940	12,248
Deferred rent	3,601	4,930
Payments made	(20,861)	(32,988)
Interest accretion	2,074	4,830
Balance as of end of period	$ 113,686	$ 112,932