Shareholders' Equity (Narrative) (Details)		1 Months Ended	3 Months Ended
	Feb. 16, 2018 USD ($) $ / shares shares	Mar. 31, 2018 shares	Mar. 31, 2019 USD ($) vote stock_class $ / shares shares	Mar. 31, 2018 USD ($) $ / shares	Dec. 31, 2018 vote $ / shares shares	Jul. 30, 2018 USD ($)	Sep. 06, 2011 USD ($)
Shareholders' Equity [Line Items]
Number of classes of common stock | stock_class			3
Preferred stock, authorized shares			500,000.0		500,000.0
Preferred stock, par value (in dollars per share) | $ / shares			$ 0.01		$ 0.01
Preferred stock, issued shares			0		0
ESOP Contribution, shares	1,006,061
ESOP Contribution, price per share | $ / shares	$ 22.18
Employee stock ownership plan contribution expense | $	$ 22,300,000		$ 0	$ 22,300,000.0
Dividends declared per share (in dollars per share) | $ / shares			$ 0.30	$ 0.30
Common Class A
Shareholders' Equity [Line Items]
Number of votes | vote			1		1
Share repurchase program, authorized amount | $						$ 100,000,000	$ 100,000,000
Remaining authorized repurchases | $			$ 100,000,000
Common stock, par value (in dollars per share) | $ / shares			$ 0.025		$ 0.025
Common Stock, Shares Authorized			80,000,000		80,000,000
Common Class B
Shareholders' Equity [Line Items]
Number of votes | vote			10		10
Common stock, par value (in dollars per share) | $ / shares			$ 0.025		$ 0.025
Common Stock, Shares Authorized			80,000,000		80,000,000
Common Class B | Treasury Stock
Shareholders' Equity [Line Items]
Conversion of Stock, Shares Converted		284,845
Common Class C
Shareholders' Equity [Line Items]
Number of votes | vote			10		10
Common stock, par value (in dollars per share) | $ / shares			$ 0.025		$ 0.025
Common Stock, Shares Authorized			20,000,000		20,000,000