Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2017

Equity [Abstract]

Schedule Of Capital Stock

Changes to the number of shares of capital stock issued were as follows:

	Common stock issued		Exchangeable shares issued
	Class A	Class B(1)	Class A	Class B
	(Share amounts in millions)
Balance at December 31, 2014	2.6	169.9	2.9	17.6
Shares issued under equity compensation plans	—	1.0	—	—
Shares exchanged for common stock	—	1.6	—	(1.6	)
Balance at December 31, 2015	2.6	172.5	2.9	16.0
Shares issued from public offering	—	29.9	—	—
Shares issued under equity compensation plans	—	0.5	—	—
Shares exchanged for common stock	—	0.8	—	(0.8	)
Balance at December 31, 2016	2.6	203.7	2.9	15.2
Shares issued under equity compensation plans	—	0.5	—	—
Shares exchanged for common stock	—	0.5	—	(0.5	)
Balance at December 31, 2017	2.6	204.7	2.9	14.7

(1) During 2016, we received proceeds of approximately $2.5 billion, net of issuance costs from our February 3, 2016, equity offering of 29.9 million shares of our Class B common stock. See "Class B Common Stock Equity Issuance" below for further discussion. During 2015, we repurchased Class B common shares which results in a lower number of outstanding shares compared to issued shares. See "Share Repurchase Program" below for further discussion. For all other classes, issued shares equal outstanding shares.