Capital Stock (Details)				3 Months Ended				6 Months Ended		12 Months Ended
	Aug. 02, 2017 $ / shares	Feb. 03, 2017 USD ($) $ / shares	Jan. 02, 2017 $ / shares	Jun. 30, 2017 USD ($) $ / shares shares	Mar. 31, 2017 USD ($) $ / shares	Jun. 30, 2016 USD ($) $ / shares shares	Mar. 31, 2016 USD ($) $ / shares	Jun. 30, 2017 USD ($) $ / shares shares	Jun. 30, 2016 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Feb. 24, 2016 USD ($)	Dec. 31, 2015 shares	Oct. 13, 2014 USD ($)	Dec. 31, 2012 shares
Class of Stock [Line Items]
Preferred stock authorized (shares)				40,000,000				40,000,000		40,000,000
Preferred stock par value (usd per share) | $ / shares				$ 0.001				$ 0.001		$ 0.001
Treasury stock (shares)				14,102,185				14,102,185		14,102,453
Treasury stock acquired (shares)										6,432,455
Common stock repurchases | $								$ 0		$ 232,000,000
Share price (usd per share) | $ / shares										$ 36.08
Remaining authorized repurchase amount | $				$ 168,000,000				168,000,000
Special dividends declared to shareholders and warrant holders, $5.77 per share | $				$ 21,816,000	$ 21,742,000	$ 22,959,000	$ 23,215,000	$ 43,558,000	$ 46,174,000
Number of shares called by each warrant (shares)				1				1
Regular Cash Dividend
Class of Stock [Line Items]
Dividends declared per common share (usd per share) | $ / shares				$ 0.25	$ 0.25	$ 0.25	$ 0.25	$ 0.5	$ 0.50
Regular Cash Dividend | Subsequent Event
Class of Stock [Line Items]
Dividends declared per common share (usd per share) | $ / shares	$ 0.25
Special Cash Dividend
Class of Stock [Line Items]
Dividends declared per common share (usd per share) | $ / shares			$ 5.77	0.00		$ 0.00		$ 5.77	$ 0.00
Common stock dividends (usd per share) | $ / shares		$ 5.77
Special dividends declared to shareholders and warrant holders, $5.77 per share | $		$ 499,000,000						$ 499,107,000
Regular Cash Dividend Restriction
Class of Stock [Line Items]
Dividends declared per common share (usd per share) | $ / shares				$ 0.25
Warrant
Class of Stock [Line Items]
Warrants issued (shares)				83,384				83,384						16,789,972
Warrant, exercise price, per share (usd per share) | $ / shares				$ 0.001				$ 0.001
Class A Common Stock
Class of Stock [Line Items]
Common stock, authorized (shares)				1,000,000,000				1,000,000,000		1,000,000,000
Common stock, par value (usd per share) | $ / shares				$ 0.001				$ 0.001		$ 0.001
Common stock, conversion ratio								1
Number of warrants exercised (shares)				16,373		31,958		44,848	132,066
Number of shares received				16,373		31,958		44,848	132,066
Number of shares of common stock issued (shares)				101,284,525				101,284,525		100,416,516
Shares authorized (shares) | $											$ 400,000,000		$ 400,000,000
Treasury stock acquired life to date (shares)												7,670,216
Class B Common Stock
Class of Stock [Line Items]
Common stock, authorized (shares)				1,000,000,000				1,000,000,000		1,000,000,000
Common stock, par value (usd per share) | $ / shares				$ 0.001				$ 0.001		$ 0.001
Common stock, conversion ratio								1
Number of shares converted (shares)								0	0
Number of warrants exercised (shares)								0	0
Number of shares of common stock issued (shares)				5,605				5,605		5,605
Preferred Stock
Class of Stock [Line Items]
Preferred stock authorized (shares)				40,000,000				40,000,000