Income Taxes - Components of Deferred Income Tax Assets (Liabilities) (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Deferral of book costs	$ (1,575)	$ (1,748)
Property and equipment	0	(1,807)
Pension	(11,113)	(10,566)
Other	(1,972)	(1,189)
Gross deferred tax (liabilities)	(14,660)	(15,310)
Deferred revenue	10,082	10,902
Accounts receivable	910	3,551
Property and equipment	2,495	0
Legal accrual	5,796	3,455
Compensation and benefits	2,410	3,316
Stock-based compensation	19,394	20,794
Operating leases	2,189	2,386
Other assets	9,736	8,356
Other contingent liabilities	64,236	108,423
Gross deferred tax assets	117,248	161,183
Net deferred income tax asset	$ 102,588	$ 145,873