Equity Incentive Plans and Stock-Based Compensation (Details 2) - $ / shares				1 Months Ended		3 Months Ended	12 Months Ended
		Apr. 23, 2015	Apr. 24, 2014	Apr. 30, 2012	Apr. 30, 2009	Jun. 30, 2012	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Stock Compensation Plan [Member]
Stock-Based Compensation
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized			10,000,000		6,500,000	6,500,000					4,000,000
Shares available for grant
Shares available, at the beginning of the year							7,305,368		11,173,545		10,724,228
Stock options granted (in shares)							(558,426)		(500,000)		(362,335)
Stock options forfeited (in shares)							1,978,042		1,081,107		1,624,823
Stock options expired under former plans (in shares)									(412,467)		(657,878)
Nonvested equity stock and stock units granted (in shares)	[2]						(5,007,947)	[1]	(5,316,675)	[3]	(4,537,797)
Nonvested equity stock and stock units forfeited (in shares)	[2]						1,334,110		1,279,858		382,504
Shares available, at the end of the period							5,051,147		7,305,368		11,173,545
Conversion factor used to calculate the decrease in the number of shares available for grant resulting from the grant of restricted stock awards							1.5		1.5		1.5
Conversion factor used to calculate the increase in the number of shares available for grant resulting from the forfeiture of restricted stock awards							1.5		1.5		1.5
Potential Additional Performance Stock Units [Domain]
Shares available for grant
Nonvested equity stock and stock units granted (in shares)							394,853		300,003		238,980
Options
Shares available for grant
Stock options granted (in shares)							(558,426)		(500,000)		(362,335)
Stock options forfeited (in shares)							1,978,042		1,081,107		1,624,823
Options granted (in dollars per share)							$ 12.95		$ 12.29		$ 11.27
Expected weighted-average period for recognition of compensation cost (in years)							2 years 5 months 16 days
Employee Stock [Member]
Stock-Based Compensation
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized		2,000,000	1,500,000	1,500,000
Shares available for grant
Shares available, at the end of the period							836,273
Expected weighted-average period for recognition of compensation cost (in years)							4 months

[1] Amount includes 300,003 shares that had been reserved for potential future issuance related to certain performance unit awards discussed under the section titled "Nonvested Equity Stock and Stock Units" below.

[2] For purposes of determining the number of shares available for grant under the 2015 Plan against the maximum number of shares authorized, each restricted stock granted reduces the number of shares available for grant by 1.5 shares and each restricted stock forfeited increases shares available for grant by 1.5 shares.

[3] Amount includes 238,980 shares that had been reserved for potential future issuance related to certain performance unit awards discussed under the section titled "Nonvested Equity Stock and Stock Units" below.