Summary of Significant Accounting Policies - Adoption of ASU 2016-09 - Improvements to Employee Share-Based Payment Accounting (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Income Statement
Provision for income taxes	$ (43,082)	$ (43,429)
Statement of Cash Flows
Net cash provided by operating activities	260,161	145,828
Net cash used in financing activities	189,549	$ (1,442,012)
ASU 2016-09 Improvements to Employee Share-Based Payment Accounting | Excess tax benefits and deficiencies associated with share-based payments
Income Statement
Provision for income taxes	5,800
Statement of Cash Flows
Net cash provided by operating activities	5,800
Net cash used in financing activities	$ 5,800