Stock-Based Compensation (RSU Activity) (Details)	6 Months Ended
	Jun. 30, 2017 USD ($) $ / shares shares
RSUs
Number of Shares
Balance at the beginning of the period (in shares) | shares	871,000
Granted (in shares) | shares	538,000
Vested (in shares) | shares	(346,000)
Cancelled (in shares) | shares	(51,000)
Balance at the end of the period (in shares) | shares	1,012,000
Weighted-Average Grant Date Fair Value
Balance at the beginning of the period (in dollars per share) | $ / shares	$ 28.42
Granted (in dollars per share) | $ / shares	27.97
Vested (in dollars per share) | $ / shares	28.70
Cancelled (in dollars per share) | $ / shares	28.41
Balance at the end of the period (in dollars per share) | $ / shares	$ 28.09
Restricted Stock | Outside directors
Number of Shares
Granted (in shares) | shares	3,285
Weighted-Average Grant Date Fair Value
Granted (in dollars per share) | $ / shares	$ 30.40
Additional Disclosure
Grant-date fair value (in dollars) | $	$ 100,000