CONSOLIDATED STATEMENT OF SHAREHOLDERS' EQUITY - 9 months ended Sep. 30, 2017 - USD ($) $ in Thousands	Class A Common Stock	Paid-in Capital	Retained Earnings	Total
Balance at Dec. 31, 2016	$ 1,010	$ 2,237,866	$ 1,143,311	$ 3,382,187
Balance (in shares) at Dec. 31, 2016	102,844,477
Increase (Decrease) in Shareholders' Equity
Issuance of common stock upon vesting of restricted stock units and upon exercise of options and warrants	$ 22	2,249		2,271
Issuance of common stock upon vesting of restricted stock units and upon exercise of options and warrants (in shares)	533,208
Stock-based compensation		14,435		14,435
Cash dividends (declared $0.225 per share)			(23,218)	(23,218)
Tax withholding related to vesting of restricted stock units and exercise of stock options		(5,600)		(5,600)
Tax withholding related to vesting of restricted stock units and exercise of stock options (in shares)	(138,147)
Net income			285,050	285,050
Balance at Sep. 30, 2017	$ 1,032	$ 2,248,950	1,405,601	3,655,583
Balance (in shares) at Sep. 30, 2017	103,239,538
Increase (Decrease) in Shareholders' Equity
Cumulative effect adjustment upon adoption of ASU 2016-09 | Accounting Standards Update 2016 - 09			$ 458	$ 458